One-piece heart valve stents adapted for post-implant expansion

ABSTRACT

A prosthetic heart valve configured to replace a native heart valve and having a support frame configured to be reshaped into an expanded form in order to receive and/or support an expandable prosthetic heart valve therein is disclosed, together with methods of using same. The prosthetic heart valve may be configured to have a generally rigid and/or expansion-resistant configuration when initially implanted to replace a native valve (or other prosthetic heart valve), but to assume a generally expanded form when subjected to an outward force such as that provided by a dilation balloon or other mechanical expander.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/007,879, filed Jun. 13, 2018, now U.S. Pat. No. 10,543,085, which isa continuation-in-part of U.S. patent application Ser. No. 15/624,427,filed Jun. 15, 2017, now U.S. Pat. No. 10,485,661, which is acontinuation of U.S. patent application Ser. No. 15/190,094, filed Jun.22, 2016, now U.S. Pat. No. 10,052,200, which is a continuation of U.S.patent application Ser. No. 14/136,318, filed Dec. 20, 2013, now U.S.Pat. No. 9,375,310, which claims the benefit of U.S. Patent ApplicationNo. 61/748,022, filed Dec. 31, 2012, the entire disclosures all of whichare incorporated herein by reference for all purposes. The presentapplication is also related to U.S. patent application Ser. No.12/234,559, filed Sep. 19, 2008, entitled “Prosthetic Heart ValveConfigured to Receive a Percutaneous Prosthetic Heart ValveImplantation,” and related to U.S. patent application Ser. No.12/234,580, filed Sep. 19, 2008, entitled “Annuloplasty Ring Configuredto Receive a Percutaneous Prosthetic Heart Valve Implantation,” theentire disclosures all of which are expressly incorporated herein byreference for all purposes.

FIELD OF THE INVENTION

The present invention relates to a surgical heart valve for heart valvereplacement, and more particularly to modifications to the constructionof existing surgical heart valves to enable them to receive anexpandable prosthetic heart valve therein.

BACKGROUND OF THE INVENTION

The heart is a hollow muscular organ having four pumping chambersseparated by four heart valves: aortic, mitral (or bicuspid), tricuspid,and pulmonary. Heart valves are comprised of a dense fibrous ring knownas the annulus, and leaflets or cusps attached to the annulus.

Heart valve disease is a widespread condition in which one or more ofthe valves of the heart fails to function properly. Diseased heartvalves may be categorized as either stenotic, wherein the valve does notopen sufficiently to allow adequate forward flow of blood through thevalve, and/or incompetent, wherein the valve does not close completely,causing excessive backward flow of blood through the valve when thevalve is closed. Valve disease can be severely debilitating and evenfatal if left untreated. Various surgical techniques may be used toreplace or repair a diseased or damaged valve. In a traditional valvereplacement operation, the damaged leaflets are typically excised andthe annulus sculpted to receive a replacement prosthetic valve.

A prosthetic heart valve typically comprises a support structure (suchas a frame, ring and/or stent) with a valve assembly deployed therein.The support structure is often rigid, and can be formed of variousbiocompatible materials, including metals, plastics, ceramics, etc. Twoprimary types of “conventional” heart valve replacements or prosthesesare known. One is a mechanical-type heart valve that uses a ball andcage arrangement or a pivoting mechanical closure supported by a basestructure to provide unidirectional blood flow, such as shown in U.S.Pat. No. 6,143,025 to Stobie, et al. and U.S. Pat. No. 6,719,790 toBrendzel, et al., the entire disclosures of which are hereby expresslyincorporated by reference. The other is a tissue-type or “bioprosthetic”valve having flexible leaflets supported by a base structure andprojecting into the flow stream that function much like those of anatural human heart valve and imitate their natural flexing action tocoapt against each other and ensure one-way blood flow.

In tissue-type valves, a whole xenograft valve (e.g., porcine) or aplurality of xenograft leaflets (e.g., bovine pericardium) can providefluid occluding surfaces. Synthetic leaflets have been proposed, andthus the term “flexible leaflet valve” refers to both natural andartificial “tissue-type” valves. In a typical tissue-type valve, two ormore flexible leaflets are mounted within a peripheral support structurethat usually includes posts or commissures extending in the outflowdirection to mimic natural fibrous commissures in the native annulus.The metallic or polymeric “support frame,” sometimes called a “wireform”or “stent,” has a plurality (typically three) of large radius cuspssupporting the cusp region of the flexible leaflets (i.e., either awhole xenograft valve or three separate leaflets). The ends of each pairof adjacent cusps converge somewhat asymptotically to form upstandingcommissures that terminate in tips, each extending in the oppositedirection as the arcuate cusps and having a relatively smaller radius.Components of the valve are usually assembled with one or morebiocompatible fabric (e.g., Dacron) coverings, and a fabric-coveredsewing ring is provided on the inflow end of the peripheral supportstructure.

One example of the construction of a flexible leaflet valve is seen inU.S. Pat. No. 6,585,766 to Huynh, et al. (issued Jul. 1, 2003), in whichthe exploded view of FIG. 1 illustrates a fabric-covered wireform 54 anda fabric-covered support stent 56 on either side of a leafletsubassembly 52. The contents of U.S. Pat. No. 6,585,766 are herebyincorporated by reference in their entirety. Other examples of valve andrelated assemblies/systems are found in U.S. Pat. No. 4,084,268, whichissued Apr. 18, 1978; U.S. Pat. No. 7,137,184, which issued on Nov. 21,2006; U.S. Pat. No. 8,308,798, filed Dec. 10, 2009; U.S. Pat. No.8,348,998, filed Jun. 23, 2010; and U.S. Patent Publication No.2012/0065729, filed Jun. 23, 2011; the entire contents of each of whichare hereby incorporated by reference in their entirety.

Sometimes the need for complete valve replacement may arise after apatient has already had an earlier valve replacement for the same valve.For example, a prosthetic heart valve that was successfully implanted toreplace a native valve may itself suffer damage and/or wear and tearmany years after initially being implanted. Implanting the prostheticheart valve directly within a previously-implanted prosthetic heartvalve may be impractical, in part because the new prosthetic heart valve(including the support structure and valve assembly) will have to residewithin the annulus of the previously-implanted heart valve, andtraditional prosthetic heart valves may not be configured to easilyreceive such a valve-within-a-valve implantation in a manner whichprovides secure seating for the new valve while also having a largeenough annulus within the new valve to support proper blood flowtherethrough.

Some attention has been paid to the problem of implanting a new valvewithin an old valve. In particular, the following disclose varioussolutions for valve-in-valve systems: U.S. Patent Publication No.2010/0076548, filed Sep. 19, 2008; and U.S. Patent Publication No.2011/0264207, filed Jul. 7, 2011.

Despite certain advances in the valve-in-valve area, there remains aneed for a prosthetic heart valve which can properly replace a damagedheart valve, such as a prosthetic valve configured to replace a nativevalve via surgical implantation, but which also enable a replacementexpandable prosthetic heart valve to be deployed therein at a later timewithout loss of flow capacity. The current invention meets this need.

SUMMARY OF THE INVENTION

The invention is a prosthetic heart valve configured to receive aprosthetic heart valve, such as a catheter-deployed (transcatheter)prosthetic heart valve, therein. In one embodiment, the prosthetic heartvalve has a support structure which is substantially resistant to radialcompression (and which may be substantially resistant to radialexpansion) when deployed in the patient's native heart valve annulus toreplace the native heart valve (or to replace another prosthetic heartvalve), but is configured to be radially expandable, and/or to transformto a generally expanded and/or expandable configuration, in order toreceive a prosthetic heart valve therein, such as apercutaneously-delivered prosthetic heart valve. The transformation fromexpansion-resistant to expanded/expandable can be achieved by subjectingthe expansion-resistant support structure to an outward force, such as adilation force, which may be provided by a dilation balloon used todeploy a replacement prosthetic valve.

In one important aspect, the present application discloses specificmodifications to existing surgical valves that enable manufacturers torapidly produce a valve which accommodates valve-in-valve (ViV)procedures. Specifically, the present application contemplatesretrofitting or modifying components within existing commercial surgicalvalves to enable post-implant expansion.

A preferred embodiment is a prosthetic heart valve adapted forpost-implant expansion and having an inflow end and an outflow end. Thevalve includes an inner structural support stent including a generallycircular composite band having upstanding commissure posts andcomprising an outer band surrounding and attached to an inner band thatdefines the commissure posts. The stent defines an implant circumferencethat is substantially non-compressible in normal physiological use andhas a first diameter. The outer band has at least one expandable segmentaround its periphery that permits expansion of the support stent fromthe first diameter to a second diameter larger than the first diameterupon application of an outward dilatory force from within the supportstent substantially larger than forces associated with normalphysiological use. The stent supports a plurality of flexible leafletsconfigured to ensure one-way blood flow therethrough.

In one aspect, the outer band includes a single expandable segmentlocated at either one of the cusps or one of the commissures formed byoverlapping free ends. The overlapping free ends of the outer band mayeach include at least one hole that register with one another and asuture passed through the registered holes maintain the free endsaligned but are configured to break when the support stent is subjectedto the outward dilatory force. Alternatively, the overlapping free endsof the outer band includes interlaced tabs that engage one another tomaintain alignment of the free ends and permit a limited expansion ofthe support ring. The tabs may have bulbous heads connected to the freeends by slimmer stems. Still further, the overlapping free ends of theouter band may overlap with one outside the other and a sleeve surroundsthem to maintain alignment of the free ends. Circumferential slots maybe provided along each free end that extend wider than the sleeve whenthe support stent is in the first unexpanded configuration and permitfluid flow within a cavity defined by the sleeve. In one version, theoverlapping free ends of the outer band are located below one of thecommissure posts of the inner band and the inner band further includes anotch at an inflow edge of the one commissure post to facilitate radialexpansion thereof. Still further, the overlapping free ends of the outerband may each includes at least one hole that register and a polymerelement passed through the registered holes maintains the free endsaligned but is configured to break when the support stent is subjectedto the outward dilatory force.

In a different embodiment, the expandable segment comprises at least onetab on one free end bent around the other free end. Alternatively, theexpandable segment comprises at least one tab on one free end thatprojects through a slot in the other free end. Desirably, the inner bandis a single polymer band, and the outer band is a single metallic band.The expandable segment may comprise a series of interconnected strutsconnected end-to-end by hinge-like connections which forms a zig-zagaccordion-like structure having substantially diamond-shaped cells.Alternatively, the expandable segment comprises a substantiallyserpentine structure formed by plastically-expandable struts.

In one form, the prosthetic heart valve is a two-part valve with theplurality of flexible leaflets being mounted on a detachable frame thatcouples to the support stent at the commissure posts thereof. The valvemay further include a cloth covering surrounding the support stent andfacilitating attachment of the leaflet peripheral edges along thesupport stent outflow edge. A unique identifier may be provided on thesupport stent visible from outside the body after implant thatidentifies the support stent as being expandable. A biodegradable bandmay be disposed concentrically and in close contact with the structuralstent, the biodegradable band configured to provide resistance toexpansion of the support stent after implantation which resistancelessens over time as the band degrades in the body. The prosthetic heartvalve further may have a radially-expandable inflow stent secured to andprojecting from an inflow end of the support stent, wherein theradially-expandable inflow stent has a strength requiring apredetermined expansion force to convert from a compressed state to anexpanded state, and wherein the biodegradable band is configured toprovide resistance to expansion of the support stent when thepredetermined expansion force is applied to the radially-expandableinflow stent.

The prosthetic heart valve structure may be generally rigid prior todilation, and may be configured to become generally non-rigid, and evengenerally elastic, when subjected to an outward force. The elasticitymay assist in holding a percutaneously-introduced prosthetic valvewithin the current prosthetic valve structure. The prosthetic heartvalve structure may be configured to be resistant to radial compression,but to permit radial expansion when subjected to radially expansiveforces, and potentially to even relatively small radially expansiveforces.

The prosthetic valve can be initially deployed in the patient's valveannulus using various surgical techniques (e.g., traditional open-chest,minimally-invasive, percutaneous, etc.) to correct heart valve function.If the heart valve function declines further after deployment of theprosthetic valve, a new replacement prosthetic valve can be deployedwithin the previously-deployed prosthetic valve without the need toexcise the previously-deployed prosthetic valve. Deployment of thereplacement prosthetic valve within the previously-deployed prostheticvalve can occur at a much later time from initial deployment of thepreviously-deployed prosthetic valve. The prosthetic valve of thecurrent invention is thus configured to be deployed in a patient and, ata later time, to accept and even improve deployment of a replacementprosthetic valve within the same valve annulus.

In an embodiment of the invention, the prosthetic valve is a stentedbioprosthetic valve configured to expand and contract dynamically withinthe patient's annulus. The dynamic motion of the annulus can enable thevalve opening to expand during periods of peak demand, and reduce theannular restriction to the increased flow. The expansion can alsodecrease leaflet stresses associated with potential higher gradients.The expansion can also permit later placement of an expandableprosthetic valve within the stented bioprosthetic valve. In such anembodiment, the prosthetic valve may have a set minimum radius beneathwhich it will not compress radially. The prosthetic valve may have a setmaximum radius beyond which it will not radially expand, even ifsubjected to radially expansive forces up to the 6 atm range typicallyseen in balloon catheters used to deliver and deploy balloon-expandablepercutaneously-deliverable stented prosthetic heart valves.

In an embodiment of the invention, a prosthetic valve has a compositesupport structure having a generally rigid and/or expansion-resistantportion with a substantially flexible and/or stretchable portion. Theprosthetic valve may include plastically deformable materials configuredto maintain the prosthetic valve support structure in the generallyrigid and/or expansion-resistant shape for deployment. The plasticallydeformable materials may be configured to break or otherwise plasticallydeform and no longer maintain the support structure in the generallyrigid and/or expansion-resistant configuration when subjected to adilation force. The support structure may form a continuous loop, andmay include elastically deformable material configured to providetension about the continuous loop after the support structure has beendilated by a dilation balloon or other mechanical expander.

A method for repairing a patient's heart function according to anembodiment of the invention can include: providing a prosthetic heartvalve configured to have a generally rigid and/or expansion-resistantsupport structure upon implantation and also configured to assume agenerally expanded configuration upon dilation; and implanting theprosthetic heart valve in a heart valve annulus. The method may alsoinclude deploying an expandable prosthetic heart valve within thepreviously-deployed heart valve and heart valve annulus. Deploying theexpandable prosthetic heart valve within the previously-deployedprosthetic valve and heart valve annulus may include dilating thepreviously-deployed prosthetic valve to cause the previously-deployedprosthetic valve to assume a generally expanded shape.

Dilating a previously-deployed prosthetic heart valve may include usinga dilation balloon, such as the type currently used for dilation ofnative heart valves, which can be advanced within thepreviously-deployed prosthetic heart valve and expanded to a desiredpressure and/or diameter. As a general rule, dilation balloons used fordilation of native valves are formed from generally inelastic materialto provide a generally fixed (i.e., pre-set) outer diameter wheninflated. Once such balloons are inflated to their full fixed diameter,they will not appreciably expand further (prior to rupturing) even ifadditional volume/pressure is added therein. Typical pressures forinflating such balloons are between 1 and 12, and more preferablybetween 1 and 8 atmospheres, with pre-set inflated outer diameters ofsuch balloons being on the order of 18 to 33 millimeters. The dilationballoon may be expanded to a desired pressure (e.g., 1-12 atmospheres)sufficient to fully inflate the dilation balloon to its desired diameterand to dilate and expand the previously-deployed prosthetic heart valve.

A typical surgically-implanted prosthetic heart valve will withstanddilation pressures of several atmospheres such as provided by mostdilation balloons without expanding and/or becoming elastic. Bycontrast, the prosthetic heart valve described herein is configured tobecome expanded and/or generally elastic when subjected to sufficientpressure provided by a dilation balloon or other mechanical expander. Ifthe dilation balloon is expanded, using sufficient pressure, to anexpanded outer diameter larger than the inner diameter of the prostheticheart valve of the invention, the prosthetic heart valve will expand indiameter and/or become elastic.

In one embodiment, the dilation balloon is configured with a pre-setinflated outer diameter which is larger, such as by 2 to 3 mm, or 10-20%or more, than the inner diameter of the previously-deployed prostheticheart valve. As an example, if the previously-deployed prosthetic heartvalve of the invention has an inner diameter of 23 mm, a dilationballoon having an inflated diameter of 24-27 mm may be inflated withinthe prosthetic heart valve to cause it to expand and/or become elastic.

Prosthetic heart valves according to various embodiments of theinvention can be configured to be generally rigid prior to dilation, butbecome expanded and/or elastic when subjected to a sufficient dilationpressure. For example, a prosthetic heart valve could be configured towithstand naturally occurring dilation pressures that may occur duringbeating of the heart, but to become expanded and/or elastic whensubjected to a desired pressure (e.g., from a dilation balloon), such asa pressure of 1 atmosphere, 2 atmospheres, 3 atmospheres, 4 atmospheres,5 atmospheres, or 6 atmospheres, or up to 12 atmospheres, depending onthe particular application.

In one particular embodiment of the invention, a prosthetic heart valvehas an inflow end and an outflow end, with an unexpanded configurationand an expanded configuration. A support structure defines thecircumference, and has a smaller inner diameter when the prostheticheart valve is in the unexpanded configuration and a larger innerdiameter when the prosthetic heart valve is in the second expandedconfiguration. The support structure rigidly resists inward compressionwhen the prosthetic heart valve is in the unexpanded configuration. Thevalve portion is supported by the support structure, and comprisesmultiple leaflets. When the prosthetic heart valve is in the unexpandedconfiguration each leaflet is configured to coapt with adjacent leafletsto permit blood to flow through the prosthetic heart valve, but toprevent blood from flowing through the prosthetic heart valve in theopposite direction. The support structure may have a first supportportion passing substantially around the circumference of the supportstructure and comprising a polymeric material. The first support portionmay be formed as single unitary assembly of polymeric material, and mayhave a weakened section configured to structurally fail when the supportstructure is subjected to a sufficient dilation force. The supportstructure may have a second support portion passing substantially aroundthe circumference of the support structure and formed from a metal, suchas cobalt-chromium or stainless steel. The second support portion mayhave a weakened section configured to structurally fail when the supportstructure is subjected to the same dilation force that causes theweakened section of the first support portion to fail. The dilationforce may be 2 atmospheres or more. The first support portion and thesecond support portion may be secured together at multiple points aroundthe circumference of the support structure. The first support portionweakened section and the second support portion weakened section may bepositioned adjacent each other about the circumference of the supportstructure, or may be spaced apart from each other about thecircumference of the support structure. The weakened section of thefirst support portion may comprise a thinned area of the first supportportion, and the second support portion weakened section may comprise aspot weld on the second support portion. The second support portionweakened section may comprise two openings in the second support portionwith a suture passing through the two openings. The first supportportion may comprise polyester, and the second support portion maycomprise a metal such as cobalt-chromium (Co—Cr) alloy.

A prosthetic heart valve according to the invention may further have anadditional support portion in the form of a support portion positionedat the inflow end of the prosthetic heart valve, with the third supportportion configured to radially expand into a substantially flared shapewhen subjected to a dilation force that is by itself insufficient tocause expansion of the main support structure. The third support portionmay be positioned upstream of the entire valve portion.

The first support portion may comprise a one-piece polymeric structuredefining 3 polymeric commissural supports extending lengthwise along theprosthetic heart valve and also defining 3 polymeric curved connectionsextending circumferentially about the prosthetic heart valve, whereineach curved connection connects two adjacent commissural supports, andwherein the second support portion comprises a one-piece metal structurecomprising 3 metal curved connections extending circumferentially aboutthe prosthetic heart valve, wherein the 3 metal curved connections arepositioned against and radially outside of the 3 polymeric commissuralsupports.

In a further embodiment of the invention, a prosthetic heart valve hasan inflow end and an outflow end, and has a first unexpandedconfiguration and a second expanded configuration. The valve may have asupport structure comprising multiple commissural supports with valveexpansion portions extending circumferentially between adjacentcommissural supports. The expansion portions may prevent compression ofthe support structure when the prosthetic heart valve is in theunexpanded configuration, but permit radial expansion of the supportstructure from a first diameter to a second diameter when the prostheticheart valve is subjected to a dilation force of more than 2 atmospheres.

In the expanded configuration, the leaflets of the prosthetic heartvalve (which had coapted to control blood flow prior to expansion) maynot coapt as well, or not at all. Accordingly, the leaflets(post-expansion) may permit substantial blood to flow in bothdirections. The leaflets are thus largely ineffective in controllingblood flow post-expansion. Control of the blood flow will thus beassumed by a newly implanted prosthetic valve deployed within theorifice of the prior (and now-dilated) prosthetic valve.

Expansion portions of support structures according to the invention mayhave a substantially serpentine structure formed from metal struts,wherein the metal struts have ends as well as sides, wherein adjacentmetal struts are connected in end-to-end configuration, wherein in theunexpanded configuration the metal struts are positioned side-to-sidewith sides of adjacent metal struts touching sides of adjacent metalstruts. Due to the relative thinness of current and projectedpercutaneously delivered/radially expandable prosthetic heart valves,the amount of radial expansion required of the prosthetic heart valvesdescribed herein does not have to be greater than 1 to 5 millimeters,with 2 to 3 millimeters being more typical for the embodiments herein.For example, a radial expansion of about 2 to 3 millimeters may besufficient to provide space for full deployment of a new percutaneousprosthetic valve within an existing and expanded prosthetic valve, withthe orifice of the newly deployed percutaneous prosthetic valve beingthe same size as was the orifice (pre-dilation) of theoriginally-deployed (and now dilated) prosthetic valve.

Non-limiting examples of inner diameters/orifices (pre- andpost-expansion) of embodiments of the current invention include: 15 mmwhich expands to 17 or 18 mm; 17 mm which expands to 19 or 20 mm; 19 mmwhich expands to 21 or 22 mm; 22 mm which expands to 24 or 25 mm; 25 mmthat expands to 28 mm; 27 mm that expands to 30 mm; 30 mm which expandsto 33 mm.

Valves and supports according to the embodiments of the invention may bespecifically configured to resist radial expansion until subjected to adesignated pressure, above which radial expansion may occur. Forexample, a designated pressure of 1 atm or more (e.g., 1 to 6 atm); of 2atm or more (e.g., 2 to 6 atm); of 3 atm or more (e.g., 3 to 6 atm); of4 atm or more (e.g., 4 to 6 atm); of 5 atm or more (e.g., 5 to 6 atm);or of 6 atm or more may be sufficient to trigger radial expansion.Balloon inflated pressures that will trigger expansion of valvestructures according to embodiments of the invention can range from 1atmosphere up to 10 atmospheres or even higher. However, as a practicalmatter the lower end of this range is probably more desirable. Manyballoons have a maximum rated pressure of 6 to 8 atmospheres (abovewhich there may be risk of bursting), and it thus may be desirable fordevices according to the invention to expand when subjected to pressurelower than the balloon maximum rated pressures. Accordingly, devicesaccording to the invention may be configured to radially expand whensubjected to a balloon filled to a pressure of between 4 to 5 atm, suchas 4.5 atm. Devices according to the invention may be configured toexpand when subjected to such designated expansion pressures, but onlyto expand by a selected amount (e.g., 2 to 3 millimeters)—so thatfurther radial expansion is prevented even if the pressure is increasedwell above the designated expansion pressure.

Note that the dilation balloon inflated diameters and inflatedpressures, as well as the pressures at which the prosthetic heart valvewould become expanded and/or elastic, set forth above are by way ofexample, and that the use of balloons with other pressures anddiameters, or other mechanical expanders, and of prosthetic heart valvesconfigured to change shape and/or expand and/or become elastic whensubjected to other pressures and expanded balloon diameters, are alsowithin the scope of the invention.

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a prosthetic heart valve deployed in a heart according toan embodiment of the invention;

FIGS. 2A-2C depict perspective, top, and side views, respectively, of aprosthetic heart valve according to an embodiment of the invention;

FIG. 2D depicts a top view of the prosthetic heart valve of FIGS. 2A-2Cafter the prosthetic heart valve has been dilated;

FIGS. 3A-3B depict top and side views, respectively, of a prostheticheart valve, pre-dilation, according to an embodiment of the invention;

FIGS. 3C-3D depict top and side views, respectively, of the supportstructure of FIGS. 3A-3B after the prosthetic heart valve supportstructure has been dilated;

FIGS. 4A-4B depict side views, pre-dilation and post-dilation,respectively, of a prosthetic heart valve support structure according toan embodiment of the invention;

FIGS. 5A-5D are perspective and exploded views of an exemplaryprosthetic heart valve of the prior art having inner structural bands;

FIGS. 6A-6B, 7A-7B, and 8A-8B are perspective assembled and explodedviews of different embodiments of replacement structural bands for theprior art prosthetic heart valve shown in FIG. 5A that enables the heartvalve to expand post-implantation;

FIGS. 9A-9B are perspective assembled and exploded views of analternative combination of structural bands that can be substituted intothe prior art prosthetic heart valve of FIG. 5A to enablepost-implantation expansion thereof;

FIG. 10 is a perspective view of a still further alternative moldedstructural band for substitution into the prior art prosthetic heartvalve of FIG. 5A;

FIG. 11A depicts a side view of a prosthetic heart valve support bandaccording to an embodiment of the invention;

FIGS. 11B and 11C depict side and perspective (close-up) views,respectively, of the prosthetic heart valve support band of FIG. 11Awith suture(s) securing the free ends together;

FIG. 11D shows an enlarged side view of the support band of FIG. 11Awith an alternative configuration of free ends secured together;

FIG. 11E depicts a side view of another prosthetic heart valve supportband for use with the support band of FIG. 11A;

FIG. 11F depicts a side view of a prosthetic heart valve structureformed from securing the first prosthetic heart valve support band inFIG. 11A and the second prosthetic heart valve support band in FIG. 11Einto a composite structure;

FIGS. 11G-11J show a variation on the first and second prosthetic heartvalve support bands shown in FIGS. 11A-11F;

FIGS. 11K-11N show further variations on the first prosthetic heartvalve support band;

FIGS. 12A and 12B are perspective views of another exemplary prostheticheart valve support band adapted for post-implant expansion havingoverlapping free ends with tabs that engage each other, and FIGS. 12Cand 12D are enlarged views of the overlapping free ends in bothconstricted and expanded configurations, respectively;

FIGS. 13A and 13B are perspective views of a further prosthetic heartvalve support band adapted for post-implant expansion also havingoverlapping free ends held together by a frictional sleeve, and FIG. 13Cshows the expansion of the overlapping free ends;

FIGS. 14A and 14B depict top and side views, respectively, of aprosthetic heart valve support structure according to an embodiment ofthe invention;

FIGS. 14C and 14D depict side views of a prosthetic heart valve having asupport structure as in FIGS. 14A and 14B, with a balloon catheterexpanding the expandable skirt but not expanding the main supportstructure portion;

FIGS. 14E and 14F depict top and side views, respectively, of theprosthetic heart valve support structure of FIGS. 14A and 14B after aballoon catheter has radially expanded the main support structureportion into an expanded configuration;

FIG. 15 is an exploded perspective view of an exemplary prosthetic heartvalve having an inner structural band combination that permitspost-implant expansion, and also includes a reinforcing band thatbiodegrades after implant;

FIG. 15A is an elevational view of the assembled prosthetic heart valveof FIG. 15 during a step of balloon-expanding an anchoring skirt, andFIG. 15B is a sectional view through the prosthetic heart valve during apost-implantation procedure of expanding the first valve whileimplanting a secondary heart valve therewithin;

FIGS. 16A and 16B depict perspective and top views of an expandableprosthetic heart valve with a percutaneously-deliverable expandableprosthetic heart valve stent radially expanded therein according to anembodiment of the current invention;

FIG. 16C depicts a top view of a prior art non-expandable prostheticheart valve with a percutaneously-deliverable expandable prostheticheart valve stent radially expanded therein;

FIG. 17A is a perspective view of another commercially-availablesurgical prosthetic heart valve of the prior art, and FIG. 17B is aperspective view of an inner support stent thereof;

FIGS. 18A-18D are perspective views of modifications to the innersupport stent of FIG. 17B that will enable the heart valve of FIG. 17Ato expand post-implantation;

FIG. 19A is a perspective view of another commercially-availablesurgical prosthetic heart valve of the prior art having bioprosthetictissue leaflets on the exterior thereof, and FIG. 19B is a perspectiveview of an inner support stent thereof;

FIGS. 20A-20G are perspective views of modifications to the innersupport stent of FIG. 19B that will enable the heart valve of FIG. 19Ato expand post-implantation;

FIG. 21 is a perspective view of an inner support stent of anothersurgical prosthetic heart valve;

FIGS. 22A-22D are perspective views of modifications to the innersupport stent of FIG. 21 that will enable the heart valve to expandpost-implantation;

FIG. 23A is a perspective view of another commercially-availablesurgical prosthetic heart valve of the prior art having two detachablecomponents, and FIG. 23B is a perspective view of the two componentscoupled together to form a functioning prosthetic heart valve;

FIGS. 24A-24C are perspective views of modifications to the innersupport stent of FIG. 23B that will enable a base member of the two-partheart valve of FIG. 23A to expand post-implantation;

FIG. 25A depicts an expandable prosthetic heart valve deploymentcatheter configured for expandable prosthetic heart valve deploymentaccording to an embodiment of the invention;

FIG. 25B depicts the expandable prosthetic heart valve deploymentcatheter of FIG. 25A positioned within a previously-deployed prostheticheart valve in a heart valve annulus of a patient according to anembodiment of the invention;

FIG. 25C depicts the expandable prosthetic heart valve deploymentcatheter of FIG. 25A dilating the previously-deployed prosthetic heartvalve and deploying an expandable prosthetic heart valve therewithinaccording to an embodiment of the invention;

FIG. 25D depicts the expandable prosthetic heart valve deploymentcatheter of FIG. 25A being withdrawn from the patient according to anembodiment of the invention;

FIG. 26A depicts an expandable prosthetic heart valve deploymentcatheter configured for dilation of a previously-deployed prostheticheart valve and for deployment of an expandable prosthetic heart valveaccording to an embodiment of the invention;

FIG. 26B depicts the expandable prosthetic heart valve deploymentcatheter of FIG. 26A with the dilation balloon positioned within thepreviously-deployed prosthetic heart valve in the heart valve annulusaccording to an embodiment of the invention;

FIG. 26C depicts the expandable prosthetic heart valve deploymentcatheter of FIG. 26A dilating the previously-deployed prosthetic heartvalve according to an embodiment of the invention;

FIG. 26D depicts the expandable prosthetic heart valve deploymentcatheter of FIG. 26A with the dilation balloon deflated after dilationof the previously-deployed prosthetic heart valve according to anembodiment of the invention;

FIGS. 27A and 27B are perspective and top plan views, respectively, ofan exemplary tubular adapter frame having barbs that may be used betweena previously implanted valve and a newly implanted expandable valve toenhance anchoring therebetween, and FIG. 27C is an isolation of onestrut segment thereof;

FIG. 28 is a perspective view of a portion of an alternative tubularadapter frame having horizontally-oriented barbs; and

FIG. 29A-29C schematically illustrate implant of a secondary expandablevalve within an expandable tubular adapter frame first expanded within apreviously-implanted prosthetic heart valve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The prosthetic heart valves described herein each include an internal(meaning incorporated into the valve itself as opposed to being asupplemental element) stent or frame that is generally tubular in shapeand defines a flow orifice area through which blood flows from an inflowend to an outflow end. Alternatively, the shape of the internal stentcan be oval, elliptical, irregular, or any other desired shape. Thevalves include flexible leaflets that selectively allow for fluid flowtherethrough. Thus, the flow orifice area is alternatively open andclosed via movement of leaflets.

As referred to herein, the prosthetic heart valves used in accordancewith the devices and methods of the invention may include a wide varietyof different configurations, such as a prosthetic heart valve having oneor more tissue leaflets, a synthetic heart valve having polymericleaflets, and in general any that are configured for replacing a nativeor previously implanted prosthetic heart valve. That is, the prostheticheart valves described herein can generally be used for replacement ofaortic, mitral, tricuspid, or pulmonic valves, but may also be used as avenous valve. These replacement prosthetic heart valves can also beemployed to functionally replace stentless bioprosthetic heart valves.

Various internal stents disclosed herein have “expandable segments” thatenable the stent to expand. This can occur from the expandable segmentrupturing, plastically stretching, or elastically elongating. Thus, an“expandable segment” means a location on the stent that enables it toenlarge in diameter, such as when a balloon is inflated within thestent. Examples include weak points which can rupture, thinned areasthat rupture or stretch, accordion-like structures which elongateelastically or plastically, breaks in the stent that are held togetherwith a breakable member such as a suture or spot weld, and various othermeans. The term, “expandable segment” thus encompasses each and everyone of these alternatives.

With reference to FIG. 1 , a prosthetic heart valve 10 according to theinvention is depicted in a heart 12. The heart 12 has four chambers,known as the right atrium 14, right ventricle 16, left atrium 18, andleft ventricle 20. The general anatomy of the heart 12, which isdepicted as viewed from the front of a patient, will be described forbackground purposes. The heart 12 has a muscular outer wall 22, with aninteratrial septum 24 dividing the right atrium 14 and left atrium 18,and a muscular interventricular septum 26 dividing the right ventricle16 and left ventricle 20. At the bottom end of the heart 12 is the apex28.

Blood flows through the superior vena cava 30 and the inferior vena cava32 into the right atrium 14 of the heart 12. The tricuspid valve 34,which has three leaflets 36, controls blood flow between the rightatrium 14 and the right ventricle 16. The tricuspid valve 34 is closedwhen blood is pumped out from the right ventricle 16 through thepulmonary valve 38 to the pulmonary artery 40 which branches intoarteries leading to the lungs (not shown). Thereafter, the tricuspidvalve 34 is opened to refill the right ventricle 16 with blood from theright atrium 14. Lower portions and free edges 42 of leaflets 36 of thetricuspid valve 34 are connected via tricuspid chordae tendineae 44 topapillary muscles 46 in the right ventricle 16 for controlling themovements of the tricuspid valve 34.

After exiting the lungs, the newly-oxygenated blood flows through thepulmonary veins 48 and enters the left atrium 18 of the heart 12. Themitral valve in a normal heart controls blood flow between the leftatrium 18 and the left ventricle 20. Note that in the current figure,the native mitral valve has been replaced with the prosthetic heartvalve 10, which is accordingly a prosthetic mitral valve 50. Theprosthetic mitral valve 50 is closed during ventricular systole whenblood is ejected from the left ventricle 20 into the aorta 52.Thereafter, the prosthetic mitral valve 50 is opened to refill the leftventricle 20 with blood from the left atrium 18. Blood from the leftventricle 20 is pumped by power created from the musculature of theheart wall 22 and the muscular interventricular septum 26 through theaortic valve 62 into the aorta 52 which branches into arteries leadingto all parts of the body.

In the particular embodiment depicted, the prosthetic heart valve 10 isdeployed to replace a native mitral valve, and more particularly issecured (via, e.g., sutures) adjacent and around the mitral valveannulus 64. Depending on the particular application, including themethod by which the prosthetic heart valve 10 was implanted, theparticular native valve (aortic, mitral, tricuspid, etc.) and/or some orall of its associated structures may be entirely or partially removedprior to or during implantation of the prosthetic heart valve 10, or thenative valve and/or some or all associated structures may simply be leftin place with the prosthetic heart valve 10 installed over the nativevalve. For example, a native mitral valve typically has two leaflets(anterior leaflet and posterior leaflet), lower portions and free edgesof which are connected via mitral chordae tendineae to papillary muscles60 in the left ventricle 20 for controlling the movements of the mitralvalve. Not all of these structures (i.e., mitral valve leaflets, chordaetendineae) are depicted in FIG. 1 because, in the particular embodiment,the native mitral valve and many associated structures (chordae, etc.)have been removed prior to or during implantation of the prostheticheart valve 10. However, in many prosthetic valve implantations,surgeons choose to preserve many of the chordae tendineae, etc., evenwhen excising the native valve.

Although FIG. 1 depicts a prosthetic mitral valve, note that theinvention described herein can be applied to prosthetic valves (andsystems and methods therefore) configured to replace any of the heartvalves, including aortic, mitral, tricuspid, and pulmonary valves.

FIGS. 2A-2C depict a prosthetic heart valve 70 according to anembodiment of the invention, where the prosthetic heart valve 70comprises a support frame 72 and valve structure 74. In the particularembodiment depicted, the valve structure 74 comprises three heart valveleaflets 76. The prosthetic heart valve 70 has an inner diameter 78 a ofa valve orifice 80 through which blood may flow in one direction, butthe valve leaflets 76 will prevent blood flow in the opposite direction.The support frame 72 is generally rigid and/or expansion-resistant inorder to maintain the particular shape (which in this embodiment isgenerally round) and diameter 78 a of the valve orifice 80 and also tomaintain the respective valve leaflets 76 in proper alignment in orderfor the valve structure 74 to properly close and open. The particularsupport frame 72 also includes commissure supports or posts 75 whichhelp support the free edges of the valve leaflets 76. In a preferredconstruction, each of the valve leaflets 76 attaches along a cusp edgeto the surrounding support frame 72 and up along adjacent commissureposts 75. In the particular embodiment depicted in FIGS. 2A-2C, thesupport frame 72 defines a generally rigid and/or expansion-resistantring 82 which encircles the valve 70 and defines a generally round valveorifice 80, but other shapes are also within the scope of the invention,depending on the particular application (including issues such as theparticular native valve to be replaced, etc.) The particular prostheticheart valve 70 includes visualization markers 73 (such as radiopaquemarkers, etc.), which in the current embodiment are on the support frame72 and correspond to the ring 82 and also to the commissure posts 75(and hence to the commissures), which can aid in proper placement of asubsequently-deployed expandable prosthetic heart valve within the valveorifice 80 of the prosthetic heart valve 70.

When the prosthetic heart valve 70 of FIGS. 2A-2C is subjected to adilation force (such as that from a dilation balloon, which may providepressures of 1 to 12, or more usually 1 and 8, atmospheres), theprosthetic heart valve will be expanded somewhat. The support frame 72will transition from the generally rigid and/or expansion-resistantconfiguration of FIGS. 2A-2C to a generally non-rigid and expandedconfiguration depicted in FIG. 2D. Note that the ring 82, which wasgenerally rigid and/or expansion-resistant, is now generally expanded,and the valve orifice 80 has accordingly been enlarged to a larger innerdiameter 78 b. The larger inner diameter 78 b is configured to receivean expandable prosthetic heart valve therein. The overall result is thatthe “post-dilation” prosthetic heart valve 70 of FIG. 2D has a generallylarger inner diameter circular opening 78 b. The actual inner diameterswill depend on the particular application, including aspects of theparticular patient's heart (e.g., native valve and/or annulus diameter,etc.). As an example, the pre-dilation inner diameter 78 a for a mitralvalve may be between 22-30 mm, or for an aortic valve 18-28 mm. Thepost-dilation inner diameter 78 b will be larger, and more specificallylarge enough to accommodate the outer diameter of an expandableprosthetic valve therein.

In some procedures where an expandable prosthetic heart valve is used toreplace/repair a previously-deployed prosthetic heart valve, it may bedesirable for the expandable prosthetic heart valve to have a deployed(expanded) inner diameter (and corresponding expandable prosthetic heartvalve orifice area) approximately equal to or even greater than thepre-dilation inner diameter 78 a (and corresponding pre-dilationprosthetic valve orifice area) of the previously-deployed prostheticheart valve 70. Such consistency between inner diameters/orifice areas,or improvement thereto, can be useful in maintaining proper blood flow,so that the expandable prosthetic heart valve will provide the same orimproved blood flow as was provided by the previously-deployedprosthetic heart valve. Note that the term “valve orifice area” refersto the area of the valve orifice when the valve portion is in the fullyopen configuration (e.g., with the valve leaflets in their fully openconfiguration so that the effective orifice area is at its maximumsize).

For example, Edwards Lifesciences has Sapien™ expandable prostheticheart valves having outer diameters of 23 and 26 mm, respectively, whichhave corresponding inner diameters of about 22 and 25 mm, respectively.Accordingly, the post-dilation inner diameter 78 b of the(previously-deployed) prosthetic heart valve may be on the order of 23and 26 mm (respectively) to accommodate such expandable prosthetic heartvalves. This corresponds to a post-dilation inner diameter 78 b beingabout 10 to 20% larger than the pre-dilation inner diameter 78 a.Accordingly, embodiments of the invention include a prosthetic heartvalve having a post-dilation inner diameter 78 b that is about 10, 15,or 20%, or between 5-25%, 10-20%, or 13-17% of the pre-dilation innerdiameter 78 a.

Note that the invention is not limited to the above differences betweenpre- and post-dilation inner diameters. For example, there may beapplications where much smaller and/or much larger post-dilation innerdiameters may be required. In some cases an expandable prosthetic heartvalve will have an outer diameter only slightly larger than its innerdiameter, so that less expansion of the previously-deployed prostheticheart valve inner diameter is required in order to accommodate theexpandable prosthetic heart valve. In other cases an expandableprosthetic heart valve may have an outer diameter that is much largerthan its inner diameter, so that a greater expansion of thepreviously-deployed prosthetic heart valve inner diameter is necessaryto accommodate the expandable prosthetic heart valve. There may also beapplications where it may be desirable to deploy an expandableprosthetic heart valve having a smaller or larger inner diameter thanwas provided by the (previously-deployed and pre-dilation) prostheticheart valve.

Note that, depending on the particular embodiment, a prosthetic heartvalve 70 may return to its pre-dilation inner diameter 78 a after beingsubject to dilation such as from a balloon dilation catheter or othermechanical expander. However, the dilation will have rendered the“post-dilation” prosthetic heart valve 70 into a generally non-rigidand/or expansion-friendly configuration, so that the “post-dilation”prosthetic heart valve 70 will be forced with relative ease into alarger diameter (such as 78 b) when an expandable (e.g.,balloon-expandable, self-expanding, etc.) prosthetic heart valve isdeployed within the valve orifice 80 of the prosthetic heart valve 70.

FIGS. 3A-3D depict a further embodiment of a support structure 90according to the invention, where expansion sections are formed by aseries of interconnected struts 92 connected end-to-end by hinge-likeconnections 94 to form a zig-zag accordion-like structure havingsubstantially diamond-shaped cells 96. In the non-expanded(pre-dilation) configuration (depicted in FIGS. 3A and 3B), thesubstantially diamond-shaped cells 96 are at a maximum height 98 and aminimum width 100, and the structure 90 defines a minimum sized innerdiameter 102. In the expanded (post-dilation) configuration (depicted inFIGS. 3C and 3D), the interconnected struts 92 have rotated at thehinge-like connections 94, and the substantially diamond-shaped cells 96have thus been stretched sideways and are at a minimum height 98 and amaximum width 100. The expanded structure 90 defines a maximum sizedinner diameter 102. The support structure 90 is desirablyplastically-expandable so as to initially resist expansion after implantand when subjected to normal anatomical expansion pressures. When thetime comes to implant a replacement valve within the prosthetic valvehaving the support structure 90, outward balloon or othermechanical-expander forces cause plastic deformation of theinterconnected struts 92, typically at the hinge-like connections 94.The balloon or mechanical expansion forces can be done separately fromimplantation of a subsequent valve, or expansion of thesubsequently-implanted valve can simultaneously expand the supportstructure 90.

FIGS. 4A-4B depict a further embodiment of a support structure 110according to the invention, where expansion sections 111 extend betweencommissural supports 113. The expansion sections 111 are formed by agenerally zig-zag or sinusoidal structure 112 formed by a seriessegments 114 secured at peaks 116 in a serpentine pattern. In thenon-expanded (pre-dilation) configuration of FIG. 4A, the zig-zagsegments 114 are compressed closely together, with minimal distances 118between adjacent peaks 116 (and may even have adjacent segments 114contacting each other edge-to-edge and thus preventing inwardcompression of the structure to a smaller diameter). In such aconfiguration, the support structure 110 will have a minimal(unexpanded) diameter. In the expanded (post-dilation) configuration ofFIG. 4B, the sinusoidal/zig-zags are pulled into a less compressedconfiguration, with the adjacent peaks 116 and segments 114 are spacedapart from each other, with maximum distances 118 between adjacent peaks116 and according a maximum diameter for the support structure 110.

In embodiments of the invention, such as that depicted in FIGS. 3A-4B,the geometry and materials of the structure may be configured so thatcertain loads (e.g., compressive and/or expansive pressures up to 1 or 2or even 3 atmospheres) will keep the material in its elastic region, sothat it may expand and/or compress slightly when subjected to relativelysmall compressive and/or expansive loads experienced under normalcardiac cycling, but will return to its original shape once such loadsare removed. The geometry and materials of the structure may beconfigured so that after a certain load is reached (such as 2, 3, 4, 5,or 6 atmospheres), plastic deformation will occur with permanent radialexpansion. With such plastic deformation, individual elements may “lockout” and thus prevent further radial dilation of the structure. Ingeneral, the various valve support structures herein are configured toexpand post-implant from an outward dilatory force from within thesupport structure larger than forces associated with normal use, i.e.,forces associated with the movement of the native annulus during cardiaccycling.

The present application discloses specific modifications to existingsurgical valves that enable manufacturers to rapidly produce a valvewhich accommodates valve-in-valve (ViV) procedures. Specifically, thepresent application contemplates retrofitting or modifying componentswithin existing surgical valves to enable post-implant expansion. Notonly does this convert any proven surgical valve for use in a ViVprocedure, but it also reduces design and manufacturing work.

FIGS. 5A-5D are perspective and exploded views of an exemplaryprosthetic heart valve 130 of the prior art oriented around a flow axis132. The heart valve 130 comprises a plurality (typically three) offlexible leaflets 134 supported partly by an undulating wireform 136 aswell as by a structural stent 138. The wireform 136 may be formed from asuitably elastic metal, such as a Co—Cr—Ni alloy like Elgiloy™, whilethe structural stent 138 may be metallic, plastic, or a combination ofthe two. As seen in FIG. 5B, outer tabs 140 of adjacent leaflets 134wrap around a portion of the structural stent 138 at so-calledcommissures of the valve that project in an outflow direction along theflow axis 132. A soft sealing or sewing ring 142 circumscribes an inflowend of the prosthetic heart valve 130 and is typically used to securethe valve to a native annulus such as with sutures. The wireform 136 andstructural stent 138 are visible in the figures, but are normallycovered with a polyester fabric to facilitate assembly and reduce directblood exposure after implant.

FIGS. 5C and 5D show the inner structural stent 138 in both assembledand exploded views. Although the general characteristics of theprosthetic heart valve 130 as seen in FIGS. 5A and 5B may be utilized ina number of different prosthetic heart valves, the illustratedstructural stent 138 is that used in a particular heart valve; namely,pericardial heart valves manufactured by Edwards Lifesciences of Irvine,Calif. For example, the Perimount™ line of heart valves that utilizepericardial leaflets 134 features an inner stent 138 much like thatshown in FIGS. 5C and 5D. In particular, the stent 138 comprises anassembly of two concentric bands—an outer band 144 surrounding an innerband 145. The bands 144, 145 are relatively thin in a radial dimensionas compared to an axial dimension, and both have coincident lower edgesthat undulate axially up and down around the circumference. The outerband 144 exhibits three truncated peaks between three downwardly curvedvalleys, while the inner band 145 has generally the same shape but alsoextends upward at commissure posts 146. The downwardly curved valleysare typically termed cusps 148, as seen in FIG. 5C.

In the exemplary Perimount™ valves, the outer band 144 is metallic andis formed from an elongated strip of metal bent to the generallycircular shape and welded as at 150. In contrast, the outer band 145 isformed of a biocompatible polymer such as polyester (PET) or Delrin™which may be molded, and also may be formed as a strip and bent circularand welded (not shown). Both the outer and inner bands 144, 145 featurea series of through holes that register with each other so that theassembly can be sewn together, as schematically illustrated in FIG. 5C.The wireform 136 and the commissure posts 146 of the inner band 145provide flexibility to the commissures of the valve which helps reducestress on the bioprosthetic material of the leaflets 134. However, theinflow end or base of the valve 130 surrounded by the sewing ring 142comprises the relatively rigid circular portions of the structural stent138. The combination of the metallic outer and plastic inner bands and144, 145 presents a relatively dimensionally stable circumferential baseto the valve, which is beneficial for conventional use. However, thesame characteristics of the structural stent 138 that provide goodstability for the surgical valve resist post-implant expansion of thevalve. Consequently, the present application contemplates a variety ofmodifications to the structural stent 138 to facilitate expansionthereof.

FIGS. 6A-6B, 7A-7B, and 8A-8B are perspective, assembled and explodedviews of three different embodiments of replacement structural bands forthe prior art prosthetic surgical heart valve 130 shown in FIG. 5A thatenables the heart valve to expand post-implementation. One advantage ofmodifying the structural bands from the valve 130 in FIG. 5A to expandis that the band is somewhat circumferentially decoupled from theleaflets 134. That is, when the valve expands, the perimeter edges ofthe leaflets 134 remain essentially unstretched since they are attachedto the wireform 136, which expands concurrently by hinging action at thecommissure tips. As a consequence, the leaflets 134 do not need to besignificantly stretched to expand our valves, potentially making thevalve easier to expand, especially if the leaflets are calcified and notamenable to distension. Desirably, therefore, the present applicationembodies a valve that can be expanded without needing to significantlystretch the leaflets.

In a first embodiment, FIGS. 6A-6B illustrate a structural stent 154comprising an inner band 156 concentrically positioned within an outerband 158. The shapes of the inner band 156 and outer band 158 are thesame as that shown for the corresponding bands 144, 145 in FIGS. 5C-5D.In contrast to the relatively rigid bands of the prior art, both bands156, 158 are modified to enable expansion post-implantation. In thisembodiment, the inner band 156 features a plurality of break points suchas notches 160 formed around the circumference that reduce the crosssectional area of the band at that point to a relatively small magnitudewhich can be broken or stretched with the application of sufficientoutward expansion force from within. For example, a balloon used toexpand a secondary prosthetic valve within the surgical valve mayprovide sufficient outward force to cause the inner band 156 to ruptureor stretch at the notches 160. The material of the inner band 156 may berelatively brittle so that excessive tensile forces cause the notches160 to break, or the material can be more ductile which permits thenotches 160 to plastically stretch in the manner of taffy.

In the illustrated embodiment, there are three notches 160 spaced evenlyaround the band 156 at the center of each cusp thereof. Additionally,the outer band 158 includes a plurality of accordion-like sections 162generally extending around the cusp portions thereof and separated bysmall plates 164 at the truncated peaks of the band. The plates 164enabled fixation of the outer band 158 at fixed nodes around the innerband 156, such as by using through holes that register for passage ofsutures. Expansion of the combined structural stent 154 eventuallyruptures or stretches the inner band 154 at one or more of the notches160, enabling further expansion of the assembly because of theaccordion-like sections 162. These sections 162 are desirably formed ofa plastically-expandable material such as stainless steel that assumesthe larger shape upon expansion, but depending on other aspects of thevalve in which the band 158 is used, they may be simply flexible. Thesections 162 are shown as repeating diamond-shaped struts connected attheir middle corners.

FIGS. 7A-7B and 8A-8B are similarly constructed with alternativeexpandable segments within the outer stents. For example, FIGS. 7A-7Billustrate a structural stent 166 comprising an inner band 168concentrically positioned within an outer band 170. The inner band 166has notches to permit it to break open or stretch from outwardexpansion. The outer band 168 features expandable segments including aplurality of connected struts in the shape of hexagons. Mid-cusphexagons 174 are somewhat longer than the remaining hexagons so thatgreater expansion occurs between the middle of the cusps and thecommissures. Again, plates 176 having through holes are positioned atthe commissures between each two expandable segments and provide pointsat which to anchor the inner band 166 to the outer band 168. Thestructural stent 178 in FIGS. 8A-8B has a similar inner band 180 and amodified outer band 182 with zig-zag shaped struts forming expandablesegments 184. Once again, small plates 186 at the commissures of theouter band 182 provide fixed nodes, if you will, for connection to theinner band 180.

FIGS. 9A-9B illustrate an alternative structural stent 190 that can besubstituted into the prior art prosthetic heart valve 130 of FIG. 5A toenable post-implantation expansion thereof. The stent 190 comprises aninner band 192 and a concentric outer band 194, as before. The innerband 192 features the upstanding commissures 195 and a plurality ofcusps each with multiple expandable segments 196. The outer band 194 hascusps with centered expandable segments 198 and truncated commissures200 shaped to match a portion of the commissures 195 of the inner band192. The expandable segments 196 are located along the cusps of theinner band 192 so as to register with solid wall portions of the outerband 194. In this way, the combined bands 192, 194 as seen in FIG. 9Ahas no holes therethrough, except at aligned suture holes 201 at thecommissures.

In the illustrated embodiment, the expandable segments 196, 198 on thetwo bands each comprise a pair of bent struts that connect upper andlower corners of the adjacent solid wall portions across gapstherebetween. The two struts are bent axially toward each other and willstraighten out to extend straight across the gaps when an outward forceis applied to the respective band, thus increasing the band diameter.Again, the material may be plastically-deformable so as to assume a newshape when expanded, or may be simply elastic and permit expansion.Also, one of the bands may be plastically-deformable such as stainlesssteel and the other plastic which merely expands along with the metalband and possesses some small amount of recoil.

FIG. 10 is a still further alternative molded structural stent 202 forsubstitution into the prior art prosthetic heart valve 130 of FIG. 5A.In this embodiment, an outer “band” 204 concentrically surrounds aninner “band” 206, the two bands actually being molded together and notbeing separable. The continuous inflow (lower) end of the stent 202includes the aforementioned alternating cusps and commissures, and thetwo “bands” 204, 206 have upper and lower notches 208 at the cuspmidpoints to enable the stent to break or stretch and expand from anoutward force. More particular, the cross-section of the stent 202 atthe notches 208 is sufficiently large to maintain the shape of the valveduring normal use in a surgical valve, but is small enough to easilybreak when a balloon, for example, is expanded within the valve of whichthe stent 202 is a part. Through holes 210 are desirably provided alongthe stent commissures to permit connection to surrounding structures,such as leaflets, a wireform, or a sewing ring.

It should be noted again that the various expandable segments disclosedherein can be substituted into any of the stents or stent bands shown.For instance, the notches 208 in FIG. 10 could be replaced with any ofthe expandable segments disclosed, such as the bent struts of theexpandable segments 196, 198 shown in FIG. 9B. Also, although notches208 are shown at the middle of each cusp of the stent 202, only onebreak point could be provided, as shown below, or the notches 208 couldbe placed at locations other than mid-cusp. The reader will understandthat numerous configurations and combinations are possible.

FIGS. 11A-11F depict another composite support stent 240 for aprosthetic heart valve formed form an inner or first band 242 and anouter or second band 244. With reference to FIGS. 11A-11B, the firstband 242 comprises a single, unitary piece of material forming asubstantially circular support structure having 3 curved segments 246connected at commissural points 248. One of the curved segments 246 hasa break 250 in the middle thereof with holes 252 drilled in the freeends 254 on either side of the break 250. As shown in FIGS. 11B and 11C,when assembled the free ends 254 are joined together via a suture 256,such as silk 4-0 suture, passed through the holes 252 and secured in aknot 258. Note that the knot 258 may be formed on the radial exterior ofthe first support structure to help maintain a smooth interior surfacethereof. FIG. 11D shows an enlarged side view of the outer support band242 of FIG. 11A with an alternative configuration of free ends 254secured together. In particular, each free end 254 has a series of holes252, three as illustrated, that align with the same number of holes inthe other free end. A length of suture 256 or other such filament may beinterlaced through the holes 252 such as in a “FIG. 8 ” configuration,and then tied off at knot 258. In testing, the arrangement in FIG. 11Dproduced an average breaking pressure of about 2.58 atm, with a range ofbetween 2.25 to 3 atm.

The suture/hole combination forms a weakened spot on the first band 242,where the suture 256 will break before the remaining parts of thesupport portion will fail when the support portion is subjected to adilation force. Note that other techniques and assemblies may be used toform the weakened portions, such as spot welds, thinned sections, andother methods such as those disclosed herein for other embodiments. Inthis particular embodiment depicted in FIGS. 11A-11B, the first band 242is desirably formed from a metal such as stainless steel orcobalt-chromium (Co—Cr).

FIG. 11E depicts a second support band 244 according to an embodiment ofthe invention. The support band 244 comprises a single, unitary piece ofa material, such as a polymer like polyester, forming a substantiallycircular support structure having 3 curved segments 260 connected atcommissural supports 262. One of the curved segments 260 has a thinnedsection 264 to form a weakened section that will fail prior to the restof the structure when subjected to a sufficient dilatation force. Notethat other methods of forming the weakened section are also within thescope of the invention, such as using spot welds, sonic welds, sutures,and/or thinned/weakened areas.

FIG. 11F depicts a composite prosthetic heart valve support stent 240formed from securing the first prosthetic heart valve support band 242and the second prosthetic heart valve support band 244 into a compositestructure. The support portions 242, 244 may be secured together viavarious techniques, such as welds, adhesives, etc. In the particularembodiment depicted, the support portions 242, 244 are secured togethervia sutures 272 adjacent the commissural points 248 and commissuralsupports 262 of the support portions 242, 244. Note that in thisparticular embodiment, the first support band 242 is positionedconcentrically within the second support band 244, and the weakened area264 of the second band 244 is positioned adjacent the suture 256 overthe overlapping ends 254 in the first band 242, so that when the secondsupport band 244 and the first support band 242 break due to dilationthe respective breaks will be at the same position around thecircumference of the support stent 240.

In an alternate embodiment, the weakened area 264 might becircumferentially displaced from the suture 256 and overlapping ends254, such as being position anywhere from a few degrees to beingcompletely opposite (i.e., 180 degrees) away around the circumference.The weakened area 264 of the second support band 244 may becircumferentially displaced from the suture 256/overlapping ends 254,but still positioned between the same pair of commissure posts 262between which the suture 256 overlapping ends 254 are positioned. Notethat one or both of the first and second support bands 242, 244 may havemultiple weakened areas designed to fail when subjected to sufficientradial pressure. For example, the first support band 242 may have asingle weakened area in the form of the suture 256 and overlapping ends254, with the second support band 244 having multiple weakened areas 264(such as 3 different weakened areas, with one weakened area beingpositioned between each pair of commissural posts 262). The offsettingof the weakened areas of the first and second support portions mayimprove the structural integrity of the structure post-dilation.

FIGS. 11G-11J show a variation on the first and second prosthetic heartvalve support bands shown in FIGS. 11A-11F in which an outer or firstband 265 includes the aforementioned undulating cusps 266 and truncatedcommissures 267, and is formed from a single element having two freeends 268 a, 268 b adjacent one of the commissures rather than at a cusp.When registered with an inner or second band 269, sutures 270 may beused to secure the registered commissure regions together such as byusing aligned holes to form a composite stent 271, as seen in FIG. 11J.After assembly into a prosthetic heart valve, such as the valve 130 ofFIG. 5A, the stent 271 initially provides good circumferential supportfor the valve and resists both compression or expansion from naturalcardiac cycling forces. At some future date, if the valve requiresreplacement, a balloon or other mechanical expander may be advanced tothe annulus and inserted into the orifice defined within the valve. Thesutures 270 at the valve commissure having the free ends 268 a, 268 bwill ultimately break from the outward expansion force of the balloon,permitting the valve to expand. Preferably the inner band 269 is made ofa polymer that possesses relatively little resistance to the balloonforces, and eventually will stretch and even rupture. To facilitate thisprocess, one or more small notches 272 such as seen in FIG. 11I may beprovided at the bottom edge of the commissure of the inner band 269.Locating the break point at one of the commissures has an added benefitof allowing the valve to expand without changing much thecircumferential spacing of the commissure posts. That is, in valveshaving three posts (and three leaflets) spaced apart 120°, for example,the lower cusps 266 of the outer band 265 will slide apart slightly, aswill the cusp portions of the inner band 269, but the upstanding postswill remain essentially in the same position. The expansion magnitude isnot so great as to distort the structure, and so the upstanding posts ofthe primary valve will remain 120° apart so as not to interfere with thefunctioning of a secondary valve or affect the ability of the valvesinuses (in aortic valves) to move and facilitate flow.

FIG. 11J shows a different stitch used with the sutures 270 holding thetwo bands 265, 269 together (relative to the more robust “Y-stitch” seenin FIG. 11F, for example). The sutures 270 are instead only loopedthrough the aligned holes and around the lower edge of the two bands265, 269 to form an “I-stitch.” This facilitates expansion of thecombined stent 271, as the sutures 270 permit relative movement/pivotingof the two bands 265, 269. In testing, the I-stitch arrangement in FIG.11J produced an average breaking pressure of about 3.08 atm, with arange of between 2.75 to 3.5 atm.

FIGS. 11G-11J also illustrate an outer band 265 that is modified so asto be readily identifiable in the body, post-implant. As mentionedelsewhere, one advantageous configuration disclosed herein is a slightmodification of an existing commercial surgical prosthetic heart valveto be expandable, which reduces development costs as well as generallylimiting the need for new assembly procedures. However, it is desirableto provide a simple and definitive indication to a surgeon years laterafter implant that the particular valve has the capacity for expansion.Therefore, the typically metal band 265 may be slightly modified to havea unique characteristic feature visible under external imagingtechniques (e.g., X-ray, CT scan, fluoroscopy, transthoracicechocardiography (TTE), or transesophageal echocardiography (TEE) thatsignifies its type. In FIGS. 11G-11J, the outer band 265 has smalldepressions or concavities formed at the peaks of the truncatedcommissures 267, which is distinct from the regular convex peaks such asthose seen at the commissures of the band 144 in the prior art valve ofFIGS. 5A-5D. This alteration takes advantage of the relatively largesurface area of the outer band 265 in the commissure areas withoutaffecting valve function.

The particular metal used for the outer band 265 in the prior art is aCr—CO alloy, which is readily visible under imaging, and thus anidentifiable shape or pattern on the band can indicate the capacity forexpansion. Other embodiments for identifying the band 265 as beingexpandable, as opposed to a non-expandable “regular” band, is to utilizesutures 270 that are highly visible with external imaging techniques.For instance, the sutures 270 could be radiopaque. Another possibilityis to use the element tantalum as a marker, either as a spot marker onthe band 265, a wire connected thereto or to another part of the valve,or the like. Tantalum is highly inert and also radiopaque, and could bespot welded to the metal band 265 to indicate a valve series or type. Astill further embodiment is to seed a permeable element of the valvewith a radiopaque compound, such as adding barium sulfate to the sewingring surrounding the band 265. Various other marking strategies arecontemplated.

FIGS. 11K-11M show further variations on the first prosthetic heartvalve support band 265. A modified outer band 265′ in FIG. 11K includestwo free ends at one of the cusps 266′ that remain aligned with severalwrap-around tabs (not numbered). The tabs of one free end that initiallyextend axially relative to the band axis may be bent around the otherfree end during assembly. Notches or shoulders on one or the otherprevents the band 265′ from being compressed, but the arrangementpermits expansion, such as with a dilation force within the valve. Intesting, the overlapping tab configuration in FIG. 11K produced anaverage breaking pressure of about 3.17 atm, with a range of between 1to 5 atm. FIG. 11L shows another modified outer band 265″ with the freeends at a cusp 266″ that overlap; one radially sliding inside the other.Instead of a flexible sleeve, as in FIGS. 13A-13B below, a suture iswrapped around multiple times, e.g., four, to maintain alignment of thetwo free ends. Furthermore, small tabs (not numbered) extend radiallyoutward from each free end to present an impediment to compression ofthe band, but the tabs are positioned and angled such that they do notunduly interfere with expansion of the band 265″. When tested for breakstrength, the configuration in FIG. 11L produced an average breakingpressure of about 3.0 atm, with a range of between 2 to 4.25 atm. FIG.11M illustrates a still further alternative band 265′″ havingoverlapping free ends at a cusp 266′″. A small tab on the inner free endpasses outward through a similar-sized slot in the outer free end,something like a belt buckle. The tab may be shaped like an arrowhead toprovide a lock of sorts and prevent its removal from the slot. Again,this limits relative movement of the two free ends to one direction thatenables expansion of the band but prevents compression. The breakstrength for the belt buckle structure in FIG. 11M is between about 6.5to 8 atm.

Finally, FIG. 11N shows a commissure portion of a still further outerband 265″″ that has a polymer rivet with male part A and female flange Bsecured through the aligned holes. The rivet A/B may be snap fittogether or fused through heating or ultrasonic welding. A variation isa polymer pin or screw that passes through the aligned holes and engagesboth free ends of the band by swaging the ends, adhesive or withthreads. The force needed to separate the ends and expand the band 265″depends on the type of polymer used. One other alternative is to formthe rivet A/B of a biodegradable material that will maintain the bandtogether for a period after implant and then dissolve, enabling easyexpansion of the band 265″. Still further, material from one of theholes may be mechanically deformed into the other hole, such as byswaging, to provide some interference which can be overcome when neededby a dilatory force. Of course, combinations of these structures arealso possible, such as combining the belt-buckle tab/slot with thewrap-around tabs.

Now with reference to FIGS. 12A-12D, a still further alternative firstor outer band 273 is shown that may be used with any of the variousexpandable heart valves disclosed herein. The band 273 has two free ends274 a, 274 b that overlap in the area of one of the cusps of the band.The free ends 274 a, 274 b include interlaced tabs 275 that permit thetwo ends to slide away from one another. In the illustrated embodiment,one free end 274 a has a pair of tabs 275 that surround a single tab onthe other free end 274 b. The tabs desirably each include an enlargedhead portion and slimmer stem, with the head portions overlappingradially and engaging at a particular outward expansion. The free ends274 a, 274 b thus prevent contraction of the band 273 and permit alimited expansion thereof. The expansion requires a relatively low forceto cause the free ends 274 a, 274 b to slide with respect to oneanother, and the band 273 is desirably coupled with an inner band with aweakened cusps, such as shown at 244 in FIG. 11E. FIGS. 12C and 12D areenlarged views of the overlapping free ends 274 a, 274 b in bothconstricted and expanded configurations, though it should be understoodthat in the expanded configuration the two ends can completely separate.The same interlaced structure may be provided at all three cusps, or atthe commissures, though the cusp regions are well suited for thestructure. When tested for break strength, the interlaced tabs in FIG.12A-12B produced an average breaking pressure of about 0.8 atm, with arange of between 0.5 to 1.0 atm.

Furthermore, the illustrated embodiment of interlaced tabs 275 shouldnot be considered limiting, and others are possible. For instance, onefree end 274 a could have 3 tine-like tabs with two outer ones extendingon one side of the other free end 274 b while a third middle one isdirected to the other side. This permits expansion but preventscontraction. Alternatively, features on the axial edges of the free ends274 a, 274 b rather than the circumferential ends could be shaped toengage each other to permit expansion but prevent contraction.

The band 273 in FIGS. 12A-12B is also modified so as to be readilyidentifiable in the body, post-implant, by external imaging. Inparticular, an arcuate upwardly convex slot (not numbered) is seen ateach commissure, just above the hole used for assembling the band 273with an inner band (not shown). Again, this readily identifiable holepattern permits a surgeon contemplating a replacement operation toeasily see that a valve-in-valve procedure is a possibility.

Finally, FIGS. 13A-13C show another “sliding” engagement wherein a firstor outer band 276 includes two overlapping free ends 277 a, 277 b thatslide with respect to one another. The free ends 277 a, 277 b aresubstantially rectangular in shape and one resides radially within andagainst the other. A sleeve 278 surrounds the free ends 277 a, 277 b andholds them radially together. The sleeve 278 desirably comprisespolyester (e.g., PET) shrink wrap tubing, or may be an elastic material,such as silicone rubber, and is shown transparent to illustrate themating free ends 277 a, 277 b. With reference to the enlargement in FIG.13C, the two free ends 277 a, 277 b may slide apart a predetermineddistance while still being overlapping. The flexible sleeve 278 providesa minimum amount of friction but generally just serves to maintainalignment of the free ends 277 a, 277 b. Each of the free ends 277 a,277 b further includes a circumferentially-oriented slot 279 that stopsshort of the terminal ends and provides a pathway for fluid flow. Asseen in FIGS. 13A and 13B, the slots 279 extend farther outward from thesleeve 278 so that fluid can always enter the spaced within the sleeve.During storage, the slots 279 permit flow of a fluid between theoverlapping free ends 277 a, 277 b to allow for sterilization. Whentested for break strength, the sleeve configuration in FIG. 13A-13Bproduced an average breaking pressure of about 1.2 atm, with a range ofbetween 0.5 to 2.0 atm. As with the rivet A/B described above, thesleeve 278 may be biodegradable to maintain alignment of the two freeends 277 a, 277 b for a period after implant and then degrades to permiteasy expansion of the band 276.

The band 276 in FIGS. 13A-13B shows a still further identifying traitvisible using external imaging and signifying it is expandable. Inparticular, a pattern of three holes are provided at each commissure.Again, this permits a surgeon contemplating a replacement operation toquickly confirm that a valve-in-valve procedure is a possibility.

FIGS. 14A and 14B depict a further embodiment of a “hybrid” prostheticheart valve 280, where an upper support stent 284 (such as the compositestent 240 in FIG. 11E) is joined by a lower frame structure 286. Thelower frame structure 286 is radially weaker than the upper supportstructure 284, and is configured to flare, as seen in FIG. 14B, whensubjected to a radially dilating pressure such as that provided by acatheter balloon 288 such as depicted in FIG. 14C. In the embodimentdepicted (and seen most clearly in FIGS. 14C-14D), the lower framestructure 286 is covered by a skirt of material 290. The prostheticheart valve 280 includes valve leaflets (not shown) to control bloodflow. The prosthetic heart valve also has a sewing ring 292 as well asthe flared lower frame structure 286/skirt 290 to assist in seating theprosthetic heart valve 280 in the desired location (e.g., a native valveannulus in a patient). Details on the initial deployment in a patient ofthe prosthetic heart valve 280 (with the upper support structure 284 inthe unexpanded configuration) are set forth in U.S. Pat. No. 8,308,798,filed Dec. 10, 2009; U.S. Pat. No. 8,348,998, filed Jun. 23, 2010; andU.S. Patent Publication No. 2012/0065729, filed Jun. 23, 2011; thecontents of which are expressly incorporated herein by reference.

The prosthetic heart valve 280 is a “hybrid” in that the upper portionis constructed similar to conventional surgical valves, with arelatively stable diameter that is not intended to be compressed orexpanded, while the lower frame structure 286 is expandable to help inanchoring the valve in place. One specific commercial prosthetic heartvalve that is constructed in this manner is one which is sold inconjunction with the Edwards Intuity™ valve system from EdwardsLifesciences of Irvine, Calif. The Edwards Intuity™ valve systemcomprises a “hybrid” valve incorporating essentially a surgicalPerimount™ valve having a stainless steel lower frame structure. Asmentioned, the valve components described above with respect to FIGS.5A-5D are essentially the same as in the Perimount™ surgical pericardialvalve sold by Edwards Lifesciences, and the modifications illustrated inFIGS. 6-14 thus enable conversion of an existing surgical valve into onethat is capable of post-implant expansion. Indeed, one especiallybeneficial aspect of the present application is disclosure of specificmodifications to existing commercial surgical valves that enablepost-implant expansion. Consequently, the present applicationcontemplates retrofitting or modifying components within existingsurgical valves to enable post-implant expansion.

A key feature of the “hybrid” valve embodiment of FIGS. 14A-14F is thatthe lower frame structure 286 will flare when subjected to a dilationpressure that is insufficient to cause radial expansion of the uppersupport structure 284, so that a user can deploy the prosthetic heartvalve 280 in the patient. For instance, a catheter balloon 288 may beused to achieve the required flaring of the lower frame structure 286,while still preserving the non-expanded nature of the upper supportstructure 284 in order to maintain the patency of the valve leaflets, asdepicted in FIGS. 14A-14B. If the prosthetic heart valve 280 should failor otherwise need replacing in the future, a balloon catheter can beintroduced into the patient, and a pressure sufficient to radiallyexpand the upper support structure 284 (e.g., by causing a failure at adesigned weakened area 296), which is also higher than that required toflare the lower frame structure 286 (such as 3 atmospheres or more), maybe applied to the prosthetic heart valve 280. With the resultingexpansion, depicted in FIGS. 14E and 14F, the entire prosthetic heartvalve 280, including the upper support portion 284 and the lower framestructure 286, are radially expanded in order to enlarge the valveorifice 294 to accommodate a new catheter-delivered prosthetic heartvalve therein. Note that, post-dilation, the lower frame structure 286may have little if any flaring, and instead has a generally constantdiameter along its length.

Note also that in another embodiment, the balloon 288 may be speciallyshaped (such as depicted in FIG. 38-40 of related U.S. PatentPublication No. 2012/0065729) so it can be positioned in such a way asto apply radially expansive pressure to the lower frame structure 286while applying little to no radially expansive pressure to the uppersupport structure. In such an embodiment, the special shaped balloon forradially expanding just the lower frame structure (e.g., during initialimplantation of the prosthetic heart valve 280) could be positioned toapply pressure only to the lower support portion. The special shapeballoon could then be expanded to a desired pressure, such as 4-5atmospheres, with the pressure being applied to expand the lower supportportion but not being applied to the upper support portion. At a latertime when it is desired to radially expand the upper support structure(e.g., when it is desired to deploy a new valve within the existingvalve), a much longer and cylindrical balloon can be used to expand boththe upper and lower structures. For example, a cylindrical balloon couldbe positioned within both the upper and lower structures and inflated tobetween 4 and 5 atmospheres, thus radially expanding both the upper andthe lower structures.

The “hybrid” type of prosthetic heart valve such as shown at 280 inFIGS. 14A-14E is implanted by advancing it into position at the annulus,and then inflating a balloon or other mechanical expander to causeoutward flaring of the lower frame structure 286. Although the uppersupport stent 284 is intended to remain with a constant diameter andonly expand later if needed when implanting a second valve directlywithin, use of a traditional cylindrical balloon can inadvertentlyexpand or distort the upper stent and possibly cause malfunction of thevalve. Therefore, the present application contemplates a temporaryreinforcing band to prevent any adverse effects to the upper stent frominitial balloon expansion, as will be explained.

FIG. 15 is an exploded perspective view of an exemplary “hybrid”prosthetic heart valve 300 having an inner structural band combination302 that permits post-implant expansion, and also includes a reinforcingband 304 that biodegrades after implant. The main structural componentsof the heart valve 300 include a plurality of flexible leaflets 310 thatare connected to and supported by a continuous undulating wireframe 312,the structural band combination 302 including an inner band 314 and anouter band 316, the reinforcing band 304, and a lower frame structure318 or anchoring skirt adapted to be expanded once implanted. Variouscloth covers and interfaces are not shown for clarity, but are typicallyused along with sutures to hold the parts together. Again, the flexibleleaflets 310 can be a combination of separate leaflets such as bovinepericardial leaflets, or a single bioprosthetic structure such as aporcine valve. The lower frame structure 318 preferablyelastically-expandable, such as being made of stainless steel, alsomaybe self-expanding in certain configurations.

The structural band combination 302 is desirably adapted to enablepost-implant expansion, much like the embodiments described above, suchas in FIGS. 6-8 . Indeed, the inner band 314 and outer band 316 areillustrated the same as those shown in FIGS. 6A-6B, though any of theexpandable band combinations can be utilized.

When the components are assembled into the valve 300, it will resemblethe valve 280 shown in FIGS. 14A-14F, and also as seen in FIG. 15A whichshows the valve during a step of balloon-expanding an anchoring skirt.Once again, this is essentially the same as the heart valve in theEdwards Intuity™ valve system. In addition to the modification thatpermits post-implant expansion, the new valve 300 features thebiodegradable reinforcing band 304. The band 304 may be madesufficiently thin and shaped the same as the outer band 316 so as to bealmost unnoticeable in the finished product. Furthermore, variousbiodegradable materials are known which are routinely included insurgical implants, and thus do not introduce any problematic materials.For example, biodegradable polymers accepted for use includePolyglycolide (PGA), PGA/Polylactide (PLA), PDS—Polydioxanone (PDS),Poly-caprolactone (PCL), Poly(dioxanone), and PGA/Tri-MethyleneCarbonate (TMC). Consequently, the modified valve 300 includesrelatively small form factor changes from the valve in the EdwardsIntuity™ valve system.

As mentioned, FIG. 15A illustrates the hybrid valve 300 isolated fromthe anatomy but shown at the moment of implantation in the annulus, suchas the aortic annulus. The valve 300 is delivered on the distal end of atubular shaft 330, such as a cannula or catheter. Although not shown, avalve holder may be utilized to couple the valve 300 to the shaft 330.An expansion member 332 such as a balloon is used to expand theanchoring skirt or lower frame structure 318 against the surroundinganatomy. For example, the frame structure 318 may be expanded to aflared shape that generally conforms to the subvalvular terrain in theleft ventricle, just below the aortic annulus. Again, the framestructure 318 is desirably plastically expandable, such as being made ofstainless steel, and holds its flared shape. Alternatively, the framestructure 318 may be self-expandable, such as being made of Nitinol,which spreads outward upon release and may apply an outward bias againstthe surrounding tissue. Also, the frame structure 318 may provide thesole means of holding the valve in place, or it may be supplemented witha small number of sutures, clips, or the like evenly distributed arounda sealing ring 333 of the valve 300. In any event, the time of theimplant process is greatly reduced from prior surgical implants by theelimination of up to 20 knot tying steps when just sutures are used.

The functional portion of the valve 300 defines an orifice diameter dthat is relatively stable by virtue of the structural band combination302, and the valve is intended to function for many years withoutproblem. However, as mentioned, occasionally the valve 300 developsissues such as calcification which reduces its effectiveness. Thisprocess may take decades, but eventually a re-operation to fix the valvemay become necessary. The modified valve 300 is designed to enabledirect expansion of a replacement valve within its orifice, theexpansion widening the valve 300 without the need to explant it.

FIG. 15B thus shows a sectional view through the prosthetic heart valve300 during a post-implantation procedure of implanting a secondary heartvalve 334 therewithin. The secondary heart valve 334 is typicallydelivered on the distal end of a balloon catheter 336 having a balloonaround which a plastically-expandable stent 340 of the secondary valveis crimped. One specific valve of this type is the Sapien™ valve sold byEdwards Lifesciences. If the primary valve 300 is implanted in theaortic annulus, the delivery shown is retrograde typically using atransfemoral access procedure, though an antegrade transapical procedureis also contemplated in which case the delivery catheter 336 would beshown entering the valve 300 from the opposite end. Such valves are alsoknown as “transcatheter” valves as they typically are introduced on theend of a catheter.

The strength of the balloon 338 expansion force is sufficient to notonly expand the secondary valve 334 outward into contact with the insideof the primary valve 300, but also to outwardly expand the primaryvalve. As mentioned with reference to FIG. 15 , the reinforcing band 304degrades over time, perhaps after 6 months to a year after implant.Consequently, the inner structural band combination 302 remains to holdthe circular shape of the valve 300. Due to the expandable character ofthe structural band combination 302, the balloon 338 can cause it tooutwardly expand to a larger diameter D as shown in FIG. 15B.Additionally, as stated elsewhere herein, any of the structural bandconfigurations disclosed in the application may be utilized or modifiedfor use as the particular structural band combination 302. Preferablythe secondary valve 334 expands to have an orifice diameter that matchesthe original orifice diameter d of the primary valve 300, which may meana total outward expansion of the primary valve of 2-4 mm, equivalent toone or two valve sizes at 2 mm increments. Preferably, the flow orificedefined by the secondary valve 334 is at least equal to the flow orificeof the primary to 300 so as to avoid any reduction of flow capacity. Theplastically-expandable stent 340 is desirably robust enough to hold theprimary valve 300 open despite any recoil forces generated by the valveor the surrounding annulus.

FIGS. 16A-16C depict expandable transcatheter heart valve frames/stents400 deployed via radial expansion within prosthetic heart valves 402,408. (While in actual practice the full transcatheter heart valve wouldbe deployed instead of just the stent, for visualization purposes onlythe stent 400 of the transcatheter valve is depicted in FIGS. 16A-16C.)In FIGS. 16A-16B, the transcatheter heart valve stent 400 is securedwithin the annulus 404 of the prosthetic heart valve 402 of the currentinvention. As seen most clearly in FIG. 16B, the stent 400 has a goodshape and the central orifice 404 has a relatively large diameter 406 toassure good blood flow therein. This larger diameter orifice which isachieved due to the expansion of the prosthetic heart valve 402 of thecurrent invention. By contrast, as depicted in FIG. 16C, if theoriginally-implanted prosthetic heart valve 408 is not radiallyexpandable, it will have less internal space to accommodate the stent400 than would be the case for the expandable embodiment of FIG. 16B.Accordingly, in the prior art embodiment of FIG. 16C the stent 400 of asubsequently installed transcatheter valve will not be able to expand toas large a diameter, and the central orifice 404 will have asignificantly smaller diameter 406 with corresponding reduction in bloodflow.

FIG. 17A is a perspective view of another commercially-availablesurgical prosthetic heart valve 410 of the prior art. The maincomponents of the heart valve 410 include an inner polymer stent 412,shown isolated in FIG. 17B, a plurality of flexible leaflets 414,typically a whole porcine valve, and a lower sewing ring 416 forsecuring the valve to an annulus. The components are typically coveredwith fabric and sewed together during manufacturing. This particularvalve 410 is sold by Medtronic, Inc. of Minneapolis, Minn. under thetrade names Hancock I™ or Hancock II™ and Mosaic™ and Mosaic Ultra™.

The inner polymer stent 412 supplies the main structural skeleton of thevalve 410, and comprises a thin-walled tubular member with a lowercircular band 418 that extends around the periphery of the stent, and aplurality of upstanding commissure posts 420. As with other conventionalvalves, there are three commissure posts 420 each of which supportsedges of two adjacent leaflets. The polymer material of the stent 412 issufficiently flexible to enable the commissure posts 420 to flex in andout somewhat during the cardiac cycle which this relieves some stressfrom the leaflets 414. However, conventional stents such as the polymerstent 412 are designed to maintain dimensional stability to the valve410, and thus are sufficiently strong that they cannot be balloonexpanded. Indeed, the Hancock II heart valve includes an embeddedtitanium ring (not shown) which further increases its resistance toexpansion. Therefore, the prior art valve 410 must be explanted when itfails to enable introduction of a replacement valve. To avoid thissituation, the present application contemplates various modifications tothe polymer stent 412 that enable it to be balloon expanded so that thevalve 410 need not be explanted.

Accordingly, FIGS. 18A-18D are perspective views of modifications to theinner support stent 412 of FIG. 17B that will enable the heart valve 410of FIG. 17A to expand post-implantation. Each of these embodimentseliminates the titanium ring embedded in the Hancock II™ valve, howeversegmented rings that are not continuous around the periphery of thestent could still be used. For the sake of clarity, similar elements inthe four different embodiments of FIGS. 18A-18D will be given the samenumbers.

In FIG. 18A, an inner support stent 422 is substantially the same as theprior art support stent 412, but includes notches 424 positioned at themid-cusp regions of the lower circular band portion 426. The “mid-cusp”location is intermediate to the upstanding commissure posts 428. Thereduction in the cross-sectional area of the band portion 426 at thesenotches 424 thus creates points of weakness which will fail when asecondary prosthetic heart valve is expanded within the primary valve.As explained above, the material of the support stent 412 may berelatively brittle so that excessive tensile forces cause the notches424 to break, or the material can be more ductile which permits thenotches 424 to plastically stretch in the manner of taffy. Variousformulations of biocompatible polymers are known with these differingphysical properties.

FIG. 18B shows an inner support stent 430 provided with expandablesegments 432 at the mid-cusp locations of the lower circular bandportion 426. In the illustrated embodiment, the expandable segments 432are similar to the expandable segments 196, 198 described above withrespect to FIGS. 9A-9B. More specifically, the expandable segments 432desirably include a pair of bent struts that connect upper and lowercorners of the adjacent solid wall portions across gaps therebetween.The two struts are bent axially toward each other and will straightenout to extend straight across the gaps when an outward force is appliedto the respective band, thus increasing the band diameter. The materialmay be plastically-deformable so as to assume a new shape when expanded,or may be simply elastic so as to permit expansion.

FIG. 18C illustrates a further support stent 434 which has twoexpandable segments 436 along each cusp part of the lower circular bandportion 426. The provision of two expandable segments 436 between eachcommissure post 428 enables greater outward expansion for the stent 434,or simply distributes the expansion around the greater circumferentialspan.

Finally, FIG. 18D depict a support stent 438 having expandable segments440 in the lower circular band portion 426 that comprise a series ofdiamond-shaped struts, similar to the accordion-like sections 162 shownin the embodiment of FIGS. 6A-6B. Indeed, any of the expandable segmentsshown in FIGS. 6-8 may be substituted for the expandable segments 440.Once again, the material of the stent 438 may be plastically-expandable,or may be the same polymer material as the prior art stent 412 whereinthe expandable segments 440 simply permit post-implant expansionthereof.

Furthermore, in conjunction with any of the stent embodiments disclosedin FIGS. 18A-18D, and indeed in conjunction with the other stentembodiments disclosed herein, a biodegradable reinforcing band such asthat shown with reference to FIG. 15 may be included for initial supportafter implantation. Such a reinforcing band will maintain dimensionalstability for the valve during the initial period of tissue overgrowth,after which the modified stents will provide sufficient structuralsupport for the valve, even though they can now be expanded by a balloonor other such expander.

FIG. 19A is a perspective view of another commercially-availablesurgical prosthetic heart valve 442 of the prior art havingbioprosthetic tissue leaflets 444 on the exterior thereof. An innersupport stent 446 that supports the leaflets 444 is shown in thepartially disassembled view of FIG. 19B. The heart valve 442 alsoincludes a sewing ring 448 and various fabric covers to assist in sewingthe components together. This valve is sold as the Trifecta™ stentedtissue valve by St. Jude Medical, Inc. of St. Paul, Minn. The innersupport stent 446 in the Trifecta™ valve is formed offatigue-resistance, high-strength titanium alloy. During assembly, thestent 446 is formed by laser cutting (e.g., from a tube),electro-polishing, and then covering the stent with a fabric prior toattaching to the sewing ring 448 and then the leaflets 444. Beingtitanium, the stent 446 may be somewhat flexible in the commissure posts449, but strongly resists radial expansion. This is an advantage for asurgical valve such as the Trifecta™ valve, as it provides gooddimensional stability. However, if the valve functioning deteriorates,and the valve must be replaced, it must be excised from the body firstbefore a secondary valve can be implanted. Consequently, the presentapplication discloses solutions for modifying the stent 446 of theTrifecta valve to permit post-implant expansion thereof.

At this stage it should be noted that the term “stent” to refer to theinner structural support of a heart valve is a term of art, andrepresents any structural element that generally providescircumferential or ring support to the valve leaflets. Sometimes suchelements are termed frames, or simply support members, and it should beunderstood that the term stent encompasses a variety of configurationsregardless of nomenclature.

FIGS. 20A-20G are perspective views of modifications to the innersupport stent 446 of FIG. 19B that will enable the Trifecta™ valve ofFIG. 19A to expand post-implantation.

In FIG. 20A, a modified stent 450 features three perforated lines 452located at the middle of each cusp region to form points ofdiscontinuity. Outward expansion of a valve having the modified stent450 will cause the stent to rupture at one or more of the perforatedlines 452, thus permitting expansion of the secondary valve within theprimary valve.

In FIG. 20B, a series of expandable segments 454 are provided around theperiphery of a modified stent 456 to enable post-implant expansion. TheTrifecta™ valve stent 446, and the modified stents shown in FIGS.20A-20G, are formed by a framework of a lower circular band 458structurally connected to an upper undulating band 460 via a pluralityof axial struts 462. For example, there are three axial struts 462 a atthe midpoint of each cusp region, and two axial struts 462 b flankingthe upstanding commissure posts 464. The upper undulating band 460defines three upstanding commissure posts 464 intermediate threedownwardly arcing cusps. Desirably, there are three separate expandablesegments 454 located in the lower circular band 458 in between and onthe outside of each pair of axial struts 462 b, as shown in FIG. 20B. Inother words, the expandable segments 454 are centered underneath thecommissure posts 464, and extend a short distance around the peripheryof the stent 456. Outward expansion force applied to a valve having themodified stent 456 will cause the expandable segments 454 to stretchout, and will also bend outward the undulating band 460 at thecommissure posts 464, as indicated by the movement arrows. Although notshown, the undulating band 460 above each of the expandable segments 454may also be expandable. This configuration helps retain the structuralintegrity of the valve during its useful life, but still provides theability to expand at some later date.

Now with reference to FIGS. 20C and 20D, modified stents 466, 468include notches or interlaced tabs around their periphery that provideweakened or rupture points (points of discontinuity) so as to enablepost-implant expansion of the stents. In FIG. 20C, interlaced tabs 470at the mating ends of a circumferential band at one of the cuspmidpoints are shown, generally where the lower band 458 and upper band460 converge. Although not shown, the mating ends with the notches orinterlaced tabs 470 may be provided at the three cusp locations.Alternatively, the stent 468 in FIG. 20D includes three notches orinterlaced tabs 472 that are located in the lower band 458 andunderneath one or more of the commissure posts 464. Expansion of a valvecontaining the stent 468 will thus cause one or more of the notches orinterlaced tabs 472 to break or separate and the commissure posts of thestent to expand, as indicated by the movement arrows.

FIG. 20E shows a single break point 474 or point of discontinuity in thelower band 458 and underneath one or more of the commissure posts 464,while FIG. 20F shows three break points 474 in the lower band 458, againunder each commissure post. The break points 474 could be simple cuts inthe lower band 458 or perforations, as mentioned above. Since the cutends of the stent at the break points 474 remain in abutment, andsurrounded by cloth or other structure that holds them in alignment,they resist radial compression of the stent at the level of the band458. On the other hand, the one-piece stent is adapted to expand at itsbase while remaining attached at the flexible commissure posts. Thisenables a valve to resist external forces applied by the implantingsurgeon or by the heart while allowing expansion of the valve when atranscatheter valve is expanded within the surgical valve.

FIG. 20G is an enlarged view of one commissure post 464 with a breakpoint 474 located directly underneath in the lower band 458. Inaddition, size markers 476 may be provided around the modified stent invarious locations, such as in the lower band 458 adjacent to thecommissure posts 464, or as seen at 477 in a cusp position.Alternatively, the size markers 476 may be located along the upper band460. Preferably, the size markers comprise symbols or alphanumericcharacters laser cut radially through the stent, which in the Trifecta™valve, as mentioned, is formed of fatigue-resistance, high-strengthtitanium alloy, although other suitable materials can also be used forthe stent, for example, stainless steel, cobalt-chromium (e.g., Elgiloyalloy), or nitinol. The through holes are thus visible in the negativeunder fluoroscopy or other viewing technologies. For instance, thenumber “21” is shown as the markers 476, 477 can indicate a valve sizeof 21 mm.

FIG. 21 is a perspective view of an inner support stent 480 of anothersurgical prosthetic heart valve of the prior art. The support stent 480may also be made of metal, such as titanium, cobalt-chromium, nitinol,or stainless steel, or a polymer such as an acetal copolymer. The stent480 includes three upstanding commissure posts 482 distributed evenlyaround a lower band 484. The lower band 484 is discontinuous below eachcommissure post 482 at a gap 485 which provides the entire structurewith some circumferential flexibility. That is, the generally circularlower band 484 maintains a generally circular base structure for theassembled valve, but permits a minor amount of circumferential expansionand contraction. This may help in the valve functioning in terms offlexing with the surrounding systolic/diastolic movement of the nativeannulus.

The one-piece stent 480 also has three sinus or cusp supports 486 thatextend away from the lower band 484 and diverge toward but do not touchthe adjacent commissure post 482. The supports 486 have two divergingside arms 488 each with a lower end attached to the lower band 484 and afree end extending toward, but not connected to, an adjacent commissurepost 482. Each support 486 is also attached to the lower band 484 at itsmidpoint so as to leave two small side windows 489.

The side arms 488 are not rigidly connected to the adjacent supportposts 482 to which they are closest. By this lack of connection the cuspsupports 486 do not unduly affect the natural flexibility/stiffness ofthe adjacent support post 482, nor affect the stress response of thefree-standing stent. However, it will be appreciated that the presenceof a tissue valve such as shown in FIG. 19A sutured to the stent 480provides an indirect tissue connection between a given commissure post482 and an adjacent side arm 488. This indirect tissue connection isbelieved useful for several reasons. First, the indirect tissueconnection between two adjacent commissure posts 482 via theintermediate cusp support structure 486 places a constraint condition onmovement of the two commissure posts. Indeed, all three commissure posts482 are similarly constrained by the indirect connection with the othertwo posts. This constraint causes the three support posts to act inunison when the valve is properly attached to the stent.

FIGS. 22A-22D are perspective views of modifications to the innersupport stent 480 of FIG. 21 that will enable the heart valve to expandpost-implantation. In FIG. 22A, the support stent 490 has short wallsegments 491 that extend toward and into abutment with each other fromthe base of each side of the commissure posts 482. The wall segments 491touch but are otherwise not connected at a point of discontinuity, so asto complete the otherwise solid lower band 484 and prevent contractionof the stent 490. At the same time, the stent 490 may be expanded at thelower band 484 such as when a transcatheter valve is expanded within thesurgical valve. There are preferably three point of discontinuitycreated by the abutting wall segments 491 below each commissure post482, though just one would permit the surgical valve to be expandedpost-implant in a valve-in-valve procedure.

FIG. 22B shows a similar stent 490 with the short wall segments 491below each commissure post 482 that come together and are only separatedby a perforated junction 492. This junction 492 provides a point ofdiscontinuity in the solid lower band 484 that again preventscontraction of the band 482 but upon breaking permits expansion.Inflation of a balloon catheter to as little as 1 atmosphere may beenough to break the perforated junction 492, or a more robust junctionmay be desired to resist up to 12 atm, for instance. FIG. 22C shows astent 490 with an expansion member 494 disposed in the gap 485 betweenthe commissure post 482 sides, in line with the solid lower band 484.Again, the expansion member 494 is preferably tightly a coiledsubstantially serpentine structure to prevent contraction of the lowerband 484 but provides a point of discontinuity that is easily expandedupon application of an inner balloon dilation force, for example. Thematerial of the expansion member 494 may be elastically or plasticallyexpandable. In one preferred embodiment, the entire stent 490 includingthe expansion members 494 are laser cut from a titanium tube. Finally,FIG. 22D shows a stent with wall segments 491 terminating in mutuallyinterlaced free ends 496 forming a point of discontinuity in the lowerband 484. The free ends 496 prevent contraction of the lower band 484but slide away from one another if subjected to an expansion force.Moreover, as with the expansion members 494, the interlaced free ends496 help maintain alignment of the lower band 484 and thus circularityof the entire lower portion of the stent 490.

As mentioned, each of the stents 490 shown could be laser cut from atube or injection molded. Alternatively, a stent 490 that has a completebase could be cut with an abrasive saw, wire EDM, water jet, machining,or some other cutting technology, or some combination of methods. Thestents 490 are preferably titanium, but may be stainless steel, Elgiloy,Nitinol, or even a polymer.

FIG. 23A shows a still further commercially-available surgicalprosthetic heart valve 504 of the prior art having two detachablecomponents—a valve leaflet subassembly 505 and a docking or base member506. FIG. 23B shows the two components coupled together to form thefunctioning prosthetic heart valve 504. These drawings represent theVitality™ or VXi™ two-piece heart valve system sold by ValveXchange,Inc. of Greenwood Village, Colo. The valve leaflet subassembly 505comprises a plurality of flexible leaflets 507 mounted to a frame thatincludes connectors 508 located at commissure areas. The base member 506primarily includes a tubular stent 509 having upstanding commissures510. The tubular stent 509 in the Vitality™ valve is a biocompatiblepolymer.

The connectors 508 of the leaflet subassembly 505 include structure formating with corresponding structure on the upstanding commissures 510 soas to form the final two-piece valve assembly 504 as seen in FIG. 23B.The system is designed to first implant the base member 506, such as bysewing it in place at the annulus, and then advancing the leafletsubassembly 505 into position and coupling the connectors 508 with thecommissures 510. Down the road, if the valve 504 becomes incompetent orotherwise as a decrease of function, the base member 506 can remain inplace while the leaflet subassembly 505 is removed and replaced with anew one. However, while this configuration obviates the need to excisethe entire valve, the procedure for removing the original leafletsubassembly 505 and connecting a new one is relatively complicated.Instead, the present application contemplates modifying the base member506 to enable it to be expanded post-implant by a secondary expandableheart valve advanced transfemorally or transapically.

FIGS. 24A-24C illustrate several modifications to the inner supportstent 509 of FIG. 23B that will enable a base member 506 of the two-partheart valve 504 of FIG. 23A to expand post-implantation.

For example, FIG. 24A shows a modified stent 511 including one or more(two shown) circular reinforcing filaments 512 embedded within thematerial of the stent and surrounding the lower portion thereof. Threebiodegradable wall segments 513 of the stent 511 are provided atapproximately the mid-cusp locations. Initially, the stent 511 functionsthe same as the stent 509 for the prior art base member 506, and hassufficient circumferential strength to maintain dimensional stabilityduring the initial tissue ingrowth period. After some time in the body,the wall segments 513 degrade, but the presence of the reinforcingfilaments 512 maintains the circularity of the stent 511. If the leafletsubassembly starts to wear out, a secondary expandable prosthetic valvemay be advanced into position within the two-piece valve and expandedoutward, whereby the filaments 512 will break, permitting the stent 511to expand. This obviates the need for removing the leaflet subassembly.

FIG. 24B illustrates another modified stent 514 which is shaped nearlythe same as the original stent 509 and made of the same material. At themid-point of the cusps, the stent 514 includes weakened regions 515 wearthe radial thickness of the wall gradually decreases to a magnitude thatpermits it to be broken or stretch upon expansion of a balloon withinthe stent. The polymer material of the stent 514 may be relativelybrittle so that the weakened regions 515 break, or the material can beductile which permits the weakened regions 515 to plastically stretch.Again, this provides good dimensional stability throughout the life ofthe leaflet subassembly, but permits introduction of a secondaryexpandable valve within the two-piece valve rather than replacing theleaflet subassembly.

Finally, alternative stent 516 shown in FIG. 24C includes threebiodegradable chordal segments 517 located in the cusp regions. Moreparticularly, the chordal segments 517 taper larger from the commissuresof the stent 516 until their maximum axial dimension at the mid-pointsof the cusps so as to be smile-shaped. The overall shape of the stent516 with the chordal segments 517 is identical to the prior art stent509. However, after some time in the body, the chordal segments 517degrade leaving relatively small cross-section cusp bridges connectingthe commissures of the stent 516 which are susceptible to rupture orstretching upon inflation of an expansion balloon therein. Again,depending on the properties of the polymer material of the stent 516 thecusp bridges will break or plastically stretch. Accordingly, when theleaflet subassembly deteriorates, a secondary expandable valve can beintroduced within the two-piece valve and expanded, breaking apart thestent 516 in the process.

Note that there are many variations of the above-cited embodiments,including numerous combinations of the various embodiments, all of whichare in the scope of the invention. Segments of one embodiment can becombined with the expandable portions of other embodiments. Also, aparticular support structure could have any combination of theabove-discussed expandable portions.

FIG. 25A depicts an expandable prosthetic heart valve deploymentcatheter 520 configured for (prior) prosthetic heart valve dilation and(replacement) expandable prosthetic heart valve deployment. Thedeployment catheter 520 has an elongated main body 522, a proximal end524, and a distal end 526. The proximal end 524 includes a handle 528.The distal end 526 includes a dilation balloon 530 upon which anexpandable prosthetic valve 532 is mounted. In the particular embodimentdepicted, the expandable prosthetic valve 532 includes a stent 534. Thedistal end 526 may also include one or more radiopaque markers 533 orsimilar visibility markers to improve visibility of the device withinthe patient when using fluoroscopy or other viewing technologies.

FIGS. 25B-25D depict deployment of an expandable prosthetic heart valve532 within a heart valve annulus 536 where a prosthetic heart valve 518has previously been deployed. The previously-deployed prosthetic heartvalve 518 may have been deployed using any methods, including methodscurrently known in the art such as traditional (open chest) surgery,minimally-invasive (e.g., keyhole) surgery, and percutaneous surgery.Depending on the particular application, the previously-deployedprosthetic heart valve 518 can be deployed in the patient years priorto, days prior to, hours prior to, or immediately prior to deployment ofthe expandable prosthetic heart valve 532 as depicted in FIGS. 25B-25D.

FIG. 25B depicts the expandable prosthetic heart valve deploymentcatheter 520 of FIG. 25A with the distal end 526 advanced so that thedilation balloon 530 and expandable prosthetic heart valve 532 arepositioned within the previously-deployed prosthetic heart valve 518 inthe patient's heart 540. The previously-deployed prosthetic heart valve518 is seen in cross-section to show the generally rigid and/orexpansion-resistant support frame 538.

In the particular embodiment depicted in FIG. 25B, the deploymentcatheter 520 has been advanced over a guide wire 542, which was advancedinto the patient's heart 540 and previously-deployed prosthetic heartvalve 518 prior to advancement of the deployment catheter 520 into thepatient. Note that the use of a guide wire 542 is optional. Other guidedevices could also be used, in addition to or in lieu of a guide wire.For example, a guide catheter could be used, wherein a guide catheter isadvanced to a desired position within a patient, and the deploymentcatheter is then advanced into the patient inside of the guide catheteruntil the distal end of the deployment catheter extends from a distalopening in the guide catheter. A deployment catheter could also be usedwithout any sort of guide wire or guide catheter, so that the deploymentcatheter is guided by itself into the desired treatment location.

As depicted in FIG. 25C, once the dilation balloon 530 and expandableprosthetic heart valve 532 are properly positioned within the heartvalve annulus 534 and previously-deployed prosthetic heart valve 518,the dilation balloon 530 is expanded. The expanding dilation balloon 530forces the stent 534 to expand outwardly, and forces the leaflets 544 ofthe previously-deployed prosthetic heart valve 518 against the heartvalve annulus 536. The force from the expanding dilation balloon 530also dilates the previously-deployed prosthetic heart valve 518 andheart valve annulus 536, forcing the support frame 538 of thepreviously-deployed prosthetic heart valve 518 to expand.

In FIG. 25D, the dilation balloon 530 is deflated or otherwise reducedin diameter, with the new expandable prosthetic valve 532 deployed inthe heart valve annulus 536 and previously-deployed prosthetic heartvalve 518, and also held in place by the stent 534. The outward pressurefrom the expanded stent 532, along with the inward pressure from theheart valve annulus 536 and from any elastic portions (such as core,cords, and/or or covers) of the previously-deployed prosthetic heartvalve 518 or from the previously-deployed prosthetic heart valveleaflets 544, combine to firmly seat the new expandable prosthetic valve532 in the desired position in the heart valve annulus 536 andpreviously-deployed prosthetic heart valve 518. The deployment catheter520 with the dilation balloon 530 can then be withdrawn from the heart540, leaving the new expandable prosthetic heart valve 532 in itsdeployed position within the patient and the previously-deployedprosthetic heart valve 518.

In a further embodiment of the invention, the previously-deployedprosthetic heart valve 518 is dilated in a separate step from deploymentof the expandable prosthetic heart valve 532. FIG. 26A depicts anexpandable prosthetic heart valve deployment catheter 520 configured forpreviously-deployed prosthetic heart valve dilation and expandableprosthetic heart valve deployment using two separate balloons, and morespecifically a distal balloon 530 a and a proximal balloon 530 b. Thedistal balloon 530 a is configured to deploy the new expandableprosthetic valve 532, which is positioned on the distal balloon 530 a,whereas the proximal balloon 530 b is configured for dilation of thepreviously-deployed prosthetic heart valve 518.

FIGS. 26B-26D depict dilation of the previously-deployed prostheticheart valve 518 and valve annulus 536 using the proximal balloon 530 b.In FIG. 26B, the deployment catheter 520 has been advanced into theheart 530 with the distal balloon 530 a (with expandable prostheticvalve 532 thereon) advanced past the previously-deployed prostheticheart valve 518, and the proximal balloon 530 b positioned within thepreviously-deployed prosthetic heart valve 518 and valve annulus 536.

The proximal balloon 530 b is inflated or otherwise expanded, asdepicted in FIG. 26C, thereby dilating the previously-deployedprosthetic heart valve 518 and valve annulus 536. The support frame 538of the previously-deployed prosthetic heart valve 518 is expanded and/orassumes a generally non-rigid configuration, similarly to the changespreviously discussed with respect to the dilation discussed in FIG. 26Cabove.

After dilation of the previously-deployed prosthetic heart valve 518,the proximal balloon 530 b is deflated or otherwise reduced in diameter,as depicted in FIG. 26D. The deployment catheter 520 may then bewithdrawn from the patient until the proximal balloon 530 b is proximalof the previously-deployed prosthetic heart valve 518 and the distalballoon 530 a is positioned within the previously-deployed prostheticheart valve 518. The distal balloon 530 a will be positioned within thepreviously-deployed prosthetic heart valve 518 in a similar fashion tothat depicted for balloon 530 in FIG. 25B. The distal balloon 530 a willthen be expanded to deploy the expandable prosthetic valve 532 inessentially the same manner as was discussed and depicted in FIGS.25B-25D. The distal balloon 530 a will serve to deploy the newexpandable prosthetic valve 532, and may also serve to further dilatethe previously-deployed prosthetic heart valve 518 and/or native valveannulus 536.

Note that in an alternate embodiment two separate catheters are used fordilating the previously-implanted prosthetic valve. The first ballooncatheter is a traditional dilation catheter and is advanced into thepatient to a position within the previously-deployed heart valve. Theballoon of the first balloon catheter is expanded to a desired pressure(e.g., 4-5 atm) sufficient to dilate (radially expand) thepreviously-implanted prosthetic valve. The first balloon catheter isthen withdrawn from the patient, and a second balloon catheter (such asthat depicted in FIGS. 25A-25D) with balloon and new expandableprosthetic heart valve thereon is advanced into the patient, the balloonis expanded to deploy the new expandable prosthetic heart valve withinthe previously-implanted (and now dilated) prosthetic heart valve, andthe second balloon catheter is withdrawn from the patient.

Note that the expandable prosthetic valve may be self-expanding, inwhich case the deployment catheter may not have a dilation balloon asdepicted in FIGS. 25A-25D and 26A-26D. Moreover, such a self-expandingprosthetic heart valve could be deployed with or without prior dilationof the previously-deployed prosthetic heart valve. For example, aself-expanding prosthetic heart valve may provide sufficient outwardradial force to dilate the previously-deployed prosthetic heart valveand/or to hold a now-dilated previously-deployed prosthetic heart valvein an expanded configuration in order to provide sufficient room for theself-expanding prosthetic heart valve in its expanded configuration.

In order for a valve-in-valve procedure to be successful, aninterference fit or some other form of anchoring is required between theinside diameter of the primary surgical valve and the outside diameterof the secondary expandable valve. Without sufficient anchoring betweenthe two valves, the secondary valve can migrate axially due to theclosing fluid pressure acting on the valve. This is particularlyimportant when a large sized expandable valve, e.g. 29 mm, deployswithin a 29 mm or larger surgical valve. With such combinations, theremay not be enough friction to secure the secondary valve within theprimary valve. Consequently, the present application contemplates animproved adapter frame to be positioned between the two valves to ensuregood anchoring.

FIGS. 27A and 27B are perspective and top plan views, respectively, ofan exemplary tubular adapter frame 600 having barbs 602 that enhanceanchoring of a newly implanted expandable valve to a previouslyimplanted valve. In the illustrated embodiment, the upper end 604 is anoutflow end, while the lower end 606 is the inflow end. As mentioned,the adapter frame 600 is advanced into the body and expanded outwardinto contact with the primary surgical valve prior to expansion of asecondary expandable valve. The barbs 602 help provide stability andresistance to migration. In a preferred embodiment, there are bothinwardly and outwardly facing barbs 602, as described below.

In the embodiment shown in FIG. 27A, the adapter frame 600 comprises anexpandable latticework of struts that may take a variety ofconfigurations. For example, the struts may comprise a series ofgenerally axially-oriented serpentine segments 612, one shown isolatedin FIG. 27C, having free ends 614 and intermediate apices 615 connectedto an adjacent segments 612. The assembly of the serpentine segments 612defines circumferential rows of connection points at and between the twoends 604, 606. In the illustrated embodiment, there are four rows ofconnection points between the adjacent axially-oriented segments 612 inthe body of the adapter frame 600 between the two ends six of four, 606.Of course, the spacing of the curves in the serpentine segments 612 andthe total length can be adjusted so that the number of rows ofconnection points may vary. The exemplary embodiment shown has 24individual serpentine segments 612 with two rows of 12 each upper barbs602 a and two rows of 12 each lower barbs 602 b.

FIG. 27A shows outwardly-directed barbs 602 a extending from theconnection points at the outflow end 604 as well as from the connectionpoints in the adjacent row. Each barb 602 a comprises a linear segmentextending from the corresponding connection point toward the inflow end606 having a small outwardly curved free end. The outwardly-directedbarbs 602 a are intended to interface with the leaflets and commissureposts of the surrounding surgical valve. Conversely, a plurality ofinwardly-directed barbs 602 b extend from the connection points at theinflow end 606 as well as from the connection points in the adjacentrow. The inwardly-directed barbs 602 b are intended to interface withthe frame struts of a secondary expandable valve. Once again, each barb602 b comprises a linear segment extending from the correspondingconnection point in having a small inwardly curved free and, but thistime the barbs are oriented toward the outflow end 604. In this way, nobarbs extend beyond either the outflow or inflow ends 604, 606.

Optionally, however, a series of inwardly-direct barbs 602 c areprovided extending from one or both of the outflow or inflow ends 604,606. For example, a plurality of barbs 602 c are shown extending fromevery other connection point on the inflow end 606 (total of six). Thisadditional row of barbs at 602 c is desirably below the bottom of thesecondary expandable valve, and in the case of an aortic implantationwould act as a “safety stop” to prevent migration of the secondary valveinto the left ventricle.

It should be understood that the tubular frame 600 itself may providesufficient friction between the two valves such that barbs are notnecessary. If barbs are used, they maybe oriented inwardly, outwardly,or both. Inwardly-direct barbs may be provided on one end, andoutwardly-directed barbs on the other hand, as shown in FIG. 27A, orthey may be interspersed throughout the frame 600. In preferredembodiments, the inwardly-directed barbs are provided on the inflow endof the frame 600, and the outwardly directed barbs are provided on theoutflow end.

FIG. 28 is a portion of an alternative tubular adapter frame 620adjacent and outflow end 604 having a number of horizontally-orientedbarbs instead of being oriented vertically. A first series of barbs 622oriented in a first circumferential direction (to the left) extend fromthe row of connection points between struts adjacent to the outflow end604. A second series of barbs 624 oriented in the oppositecircumferential direction (to the right) extend from the next row ofconnection points away from the outflow end 604. Again, these barbs at622, 624 may free ends that are curved inwardly or outwardly, but aredesirably curved outwardly adjacent the outflow end 604.

The tubular adapter frame 600 could be covered in cloth to help preventblood leakage through the open cells defined between the serpentinestruts. Preferably, a cloth with a high friction coefficient is used.Additionally, a velour type of cloth could also be used on the inside oroutside to further help prevent leakage. Another possibility is to coatthe tubular frame 600 in a soft polymer, such as silicone, such that themetallic struts are covered to reduce blood interactions and potentiallyincrease retention fiction.

The wall thickness and diameter of the tubular adapter frame 600 couldbe specific to certain combinations of primary surgical valves andsecondary expandable valves. For example, if implanting a 29 millimeterexpandable valve within a 29 mm surgical valve, the wall thickness couldbe about 0.5 mm with an outside diameter in the expanded state of theframe of about 28 mm. For a 29 mm secondary expandable valve placedwithin a 31 mm surgical valve, the wall thickness could be increased toabout 1.0 mm and the frame 600 has an outside diameter in its expandedstate of about 30 mm.

FIG. 29A-29C schematically illustrate a sequence where the adapter frame600 is used between a previously-implanted or primary prosthetic heartvalve 650 and a secondary expandable valve 652. The primary heart valve650 is shown in FIG. 29A implanted at an aortic annulus AA. In theillustrated embodiment, the heart valve 650 is shown as a modifiedPerimount™ valve manufactured by Edwards Lifesciences of Irvine, Calif.,though it is representative of a number of other surgical valves, asexplained elsewhere herein. The surgical valve 650 is modified to enablepost-implant expansion. The valve 650 typically includes a sewing ring654 through which sutures (not shown) are threaded to secure the valveto the annulus AA.

A balloon catheter 660 extends in a retrograde fashion downward from theascending aorta until a balloon 662 having the adapter frame 600 thereonis positioned directly within the valve 650. The axial height of theadapter frame 600 is shown longer than the actual height of the valve650, although a shorter frame may be effectively used.

FIG. 29B illustrate outward expansion of the balloon 662 to causecommensurate expansion of the tubular adapter frame 600 which, in turn,outwardly expands the surgical valve 650. In a preferred embodiment, themagnitude of expansion of the balloon 662 is sufficient to cause outwardexpansion of the surgical valve 650 until the inner diameter of theadapter frame 600 is at least as large as the original inner diameter ofthe surgical valve. More preferably, the balloon 662 outwardly expandsthe frame 600 to an extent that the inner diameter of the frame islarger than the original inner diameter of the surgical valve so as toenable subsequent expansion of the secondary valve they are within andend up with the same orifice size as the original valve.

Finally, FIG. 29C shows the secondary expandable valve 652 after havingbeen outwardly expanded into intimate contact with the inner surface ofthe tubular frame 600. This effectively sandwiches into a frame 600between the two valves, creating additional interference and enhancedretention force, and decreasing the likelihood of migration. This isparticularly useful for larger sized surgical valves. Again, the orificedefined by the expanded valve 652 is desirably at least as large as theoriginal inner diameter of the surgical valve 650. The secondary valve652 may be expanded using a balloon 670, as shown, or via a mechanicalexpander. Alternatively, the secondary valve 652 may be self-expanding,with the adapter frame 600 being plastically-expandable to provide arobust force holding the primary surgical valve 650 in its expandedconfiguration. A self-expanding secondary valve 652 thus comes intointimate contact with the tubular frame 600, and the frictional contacttherebetween may be supplemented by the aforementioned barbs describedabove with respect to FIGS. 27-28 .

Advantageously, the adapter frame 600 can be crimped to a relativelysmall diameter and delivered through a small catheter. Because of thesmaller profile, the adapter frame 600 and its delivery system can beintegrated into an existing secondary valve delivery catheter system. Inthat case, the overall delivery system can be advanced to align theadapter frame 600 with the existing surgical valve 650, the frame 600deployed, and then the delivery system used to advance and deploy thesecondary expandable valve 652 within the frame. All this reduces theprocedure time.

As mentioned, the frame 600 can be either plastically-expandable, suchas stainless steel or cobalt-chromium alloy, or self-expanding, such asNitinol. In the latter case, a series of loops with tethers can be usedon the distal end of the frame 600 to control expansion as it is pushedout of a catheter. However, the outward spring force of the frame 600can be made relatively low, because it is later sandwiched by thesecondary valve 652, in which case the frame does not have a greattendency to “jump” out of the catheter. A self-expanding adapter frame600 can even be made from a suitable polymer, as the spring constantrequirements are relatively low.

While the invention has been described with reference to particularembodiments, it will be understood that various changes and additionalvariations may be made and equivalents may be substituted for elementsthereof without departing from the scope of the invention or theinventive concept thereof. In addition, many modifications may be madeto adapt a particular situation or device to the teachings of theinvention without departing from the essential scope thereof. Therefore,it is intended that the invention not be limited to the particularembodiments disclosed herein, but that the invention will include allembodiments falling within the scope of the appended claims.

What is claimed is:
 1. A prosthetic heart valve adapted for post-implantexpansion and having an inflow end and an outflow end, comprising: aone-piece inner structural support stent including a generally circularsolid lower band having three upstanding commissure posts, the stentdefining an implant circumference that is substantially non-compressiblein normal physiological use and has a first diameter, and wherein thelower band is a continuous solid band except for a point ofdiscontinuity around its periphery between adjacent abutting ends of thesolid band, the adjacent abutting ends being only separated by aperforated junction defining the point of discontinuity that permitsexpansion of the support stent from the first diameter to a seconddiameter larger than the first diameter upon application of an outwarddilatory force from within the support stent substantially larger thanforces associated with normal physiological use but prevents contractionof the lower band; and a plurality of flexible leaflets supported by thestent and configured to ensure one-way blood flow therethrough.
 2. Theprosthetic heart valve of claim 1, wherein the perforated junction isconfigured to break upon application of an outward dilatory force fromwithin the support stent of at least 1 atmosphere.
 3. The prostheticheart valve of claim 1, wherein the perforated junction is configured toresist breaking until application of an outward dilatory force fromwithin the support stent of up to 12 atmospheres.
 4. The prostheticheart valve of claim 1, wherein each commissure post has a gap betweentwo sides and the lower band extends across the gaps in two wallsegments, wherein the point of discontinuity is located where the wallsegments come together defining the adjacent abutting ends.
 5. Theprosthetic heart valve of claim 1, wherein there is a single point ofdiscontinuity located below only one of the commissure posts.
 6. Theprosthetic heart valve of claim 1, wherein there is a point ofdiscontinuity located below each of the commissure posts.
 7. Theprosthetic heart valve of claim 1, further including a unique identifieron the support stent visible from outside the body after implant thatidentifies the support stent as being expandable, and the uniqueidentifier is a numerical valve size in odd 2-millimeter incrementsbetween 15-33 mm.
 8. The prosthetic heart valve of claim 1, wherein theone-piece inner structural support stent is made of titanium.
 9. Theprosthetic heart valve of claim 8, wherein each commissure post has agap between two sides and the lower band extends across the gaps in twowall segments, wherein the point of discontinuity is located where thewall segments come together defining the adjacent abutting ends.
 10. Theprosthetic heart valve of claim 1, wherein the one-piece innerstructural support stent is made of an acetal copolymer.
 11. Theprosthetic heart valve of claim 10, wherein each commissure post has agap between two sides and the lower band extends across the gaps in twowall segments, wherein the point of discontinuity is located where thewall segments come together defining the adjacent abutting ends.
 12. Aprosthetic heart valve adapted for post-implant expansion and having aninflow end and an outflow end, comprising: a one-piece inner structuralsupport stent including a generally circular solid lower band havingthree upstanding commissure posts, the stent defining an implantcircumference that is substantially non-compressible in normalphysiological use and has a first diameter, and wherein the lower bandis a continuous solid band except for a point of discontinuity aroundits periphery between adjacent ends of the solid band, the adjacent endsbeing only connected by mutually interlaced tabs defining the point ofdiscontinuity, the interlaced tabs maintaining alignment and circularityof the solid band while being arranged to slide away from one anotherand permit expansion of the support stent from the first diameter to asecond diameter larger than the first diameter upon application of anoutward dilatory force from within the support stent substantiallylarger than forces associated with normal physiological use butpreventing contraction of the lower band less than the first diameter;and a plurality of flexible leaflets supported by the stent andconfigured to ensure one-way blood flow therethrough.
 13. The prostheticheart valve of claim 12, wherein each commissure post has a gap betweentwo sides and the lower band extends across the gaps in two wallsegments, wherein the point of discontinuity is located where the wallsegments come together defining the adjacent ends.
 14. The prostheticheart valve of claim 12, wherein there is a single point ofdiscontinuity located below only one of the commissure posts.
 15. Theprosthetic heart valve of claim 12, wherein there is a point ofdiscontinuity located below each of the commissure posts.
 16. Theprosthetic heart valve of claim 12, further including a uniqueidentifier on the support stent visible from outside the body afterimplant that identifies the support stent as being expandable, and theunique identifier is a numerical valve size in odd 2-millimeterincrements between 15-33 mm.
 17. The prosthetic heart valve of claim 12,wherein the one-piece inner structural support stent is made oftitanium.
 18. The prosthetic heart valve of claim 17, wherein eachcommissure post has a gap between two sides and the lower band extendsacross the gaps in two wall segments, wherein the point of discontinuityis located where the wall segments come together defining the adjacentends.
 19. The prosthetic heart valve of claim 12, wherein the one-pieceinner structural support stent is made of an acetal copolymer.
 20. Theprosthetic heart valve of claim 19, wherein each commissure post has agap between two sides and the lower band extends across the gaps in twowall segments, wherein the point of discontinuity is located where thewall segments come together defining the adjacent ends.